With social media being the primary outlet for photographers, it has become common practice for pages, accounts, and websites with large followings to post photographer's images without permission. If an image of yours goes viral it is basically guaranteed that it's going to be used in some form without your permission. 

Sharing, Posting, and Stealing

Let me differentiate between posting and sharing. Sharing is when someone shares or retweets directly from the content creator's post. This is great as it drives traffic back to the artist, gaining them more followers and potential sales. Posting is when an image is downloaded then reposted by a person or page on their account. This does little to nothing to drive traffic to the artist. The person benefiting most from this is the owner of the page. 

The best practice for a page that wishes to post other's work is to get permission and/or include a link back to the artist's social media account or website. This gives people a link to click on right there in the description, making the post mutually beneficial for the page and artist. Often times a simple "photo by " credit is given. This is acceptable but does little in the way of driving traffic to the artist. People are lazy, if there isn't a link to click, most simply move on. The very least a page can do that won't have me sending them a cease-and-desist or reporting their account for copyright infringement is to simply leave my watermark in tact.  

The worst thing an account or website can do is to alter an image by using only a portion or cropping out the watermark while giving no credit to the artist. This was the case on Saturday when Tom Brady's facebook account posted an image of a supercell shot by Colt Forney, photoshopped into the sky over Gillette Stadium. This is blatant willful copyright infringement. As of this writing the post has over 157,000 likes and 26,000 shares with no credit to the artist. 

Colt Forney's image of a supercell in Wyoming, photoshopped over Gillette Stadium in Foxborough, Mass. 

This immediately drew the ire of weather folks, with many choosing to express their frustration on Tom Brady's post. Reading through the comments, I saw a lot of everyday people asking, "what's the big deal?" and saying, "if an image is posted online anyone can use it". This is the mindset of the average person and it is frightening.

The big deal is it's not like Colt walked out into his backyard and took his picture of that storm on a cell phone. People don't understand the amount of time, effort, and money that goes into making an image.

Here's the breakdown of costs for weather photography.

Vehicle : $20,000
Insurance  : $1,500
Fuel and maintenance : $8,698
(2015 AAA 15,000 miles at $0.58 per mile)
Hotel Costs : $2,100 (30 nights at $70 per night)
DSLR camera : $2,000
Wide angle lens : $1,500 
Telephoto lens : $1,500 
GoPro Hero x3 : $1,200
Backup DSLR : $2,000 (you wouldn't want to drive all the thousands of miles, lose a camera and be S.O.L) 
Adobe Creative Cloud : $600 ($50 per month x 12 months)

Oh, and don't forget the college degree it took to learn how to do all of the things it takes to go out and get an image like that. 

College Degree : $50,000

Grand Total $91,048

Of course this cost gets spread out over time, but that is basically the investment many storm chasers put in to do this full time. These numbers don't take into account the countless hours spent studying computer models used for forecasting, editing photos and videos, driving etc. The cost really could be higher. 

A similar incident with an image of mine. George Takei posted my image with no credit. 

Simply because your work is posted online does not give anyone free access to use it however they please. When you post an image to Facebook, you give Facebook the rights to do anything they want with your photo. They can use it for advertising. They can even sell the rights to it if they please (but has anyone ever heard of this happening?) It does not give anyone besides them the right to do anything with your photos without your permission. 

what can you do if your rights are infringed upon? 

First, try dealing with the infringer on a person-to-person basis. You could send them an invoice or request your work be removed. Well funded companies often pay a reasonable fee so the matter will be resolved. If this doesn't work, the next step is an attorney-to-infringer correspondence via a cease-and-desist letter. Sometimes just the threat of a lawsuit will end the matter.
If your images are being used without permission by somebody local it is possible to get compensated by going to small claims court. You cannot sue for copyright infringement; which may be filed only in federal court, but you may have a claim for breach of contract.
The best thing about small claims court is that you can present the case yourself. You don’t need a lawyer with you in the courtroom, although it would probably be a good idea to consult with one prior to your case. Even if you win, there is no guarantee it will be easy, or even possible, to convert the judgment to cash in your pocket. You will probably have to get the sheriff's department to execute on the judgment. Intellectual attorney Davey Jay also points out, "a suit in small claims court could get thrown out due to federal preemption". 

REGISTER YOUR IMAGES WITH THE U.S. COPYRIGHT OFFICE! This should be done long before your copyright is infringed upon. If a well funded social media account, publication, or website uses your images without your permission, and you have registered with the copyright office, you could take them to federal court and may be compensated up to $150,000 per image. If you haven't registered, it will be more difficult proving your case and your compensation will be no less than $750 and no more than $30,000 per image.  
The ISP takedown. Consider this scenario: You find your images on a website. You have registered the copyrights, but the owners of the website never requested permission to use them. They’re guilty of copyright infringement. Yet … It’s a small site, clearly with no deep pockets supporting it. You know that you could proceed with legal action, but that it will cost you plenty and you might never recoup any of it.
You attempt to contact the people running the site, requesting them to cease and desist. They don’t respond or remove your images from the site. You write them again, this time with more warning and a stronger threat of legal action. Still nothing. You don’t want your image on the site because they have no right to use it.

Under the Digital Millennium Copyright Act (DMCA), you can force the Internet Service Provider (ISP) hosting that site to remove or disable the site, so that it cannot be viewed. To do this, you must send notice to the ISP, giving the provider your name, address, and electronic signature, and a link to the infringing materials. Give enough specific information to clearly identify the copyrighted images, a statement asserting a “good faith belief” that the offender has no legal right to use the material, and a statement that you are the copyright owner or are authorized to act on the copyright owner’s behalf. You must be 100% accurate on all these counts, as this is a serious charge you’re leveling, and if you're wrong, you can open yourself up to perjury charges or monetary damages.

The ISP then informs the alleged infringer that actions have been taken, and will give the alleged infringer the chance to make a case that the site or material has been wrongly removed. If the ISP receives a proper counter-notice from the alleged infringer claiming that no infringement is taking place, they will inform you immediately. Your next step is a mandatory filing in district court of a copyright infringement lawsuit within 14 days. If you don’t file the suit, the images and the site can go right back up online.
It’s definitely not easy, but to get protection for your images you have to fight for it. Register your images. Keep good records. Be vigilant and hire a good attorney. In the long run, it’s worth it.