Photographers may want to re-read that fine print in the Terms of Service. PhotoFocus nerds consulted with their lawyers, they were alarmed to discover that every photo you share on Twitter can be sub-licensed by Twitter, or worse – all royalty-free. Their terms reveals that Twitter can do pretty much anything it wants with photos you publish via its service, and there isn’t much you can do about it. Anyone might want to be concerned because they are allowed to use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute such Content in any and all media or distribution methods that they wish.
Even those pictures of you that your friends took of you when you passed out drunk one night and they drew all over your face. YEAH, EVEN THOSE PICTURES, you might want to worry now. And here is some more bad news, you agreed that this license includes the right for Twitter to make such Content available to other companies, organizations or individuals who partner with Twitter for the syndication, broadcast, distribution or publication of such Content on other media and services, subject to our terms and conditions for such Content use.
If you are really curious whats happening to your photographs, then maybe you should have a lawyer look at the agreement terms or maybe not posting them at all on these type of sites is a good idea too.