While most of these photos are grainy, blurry and over-filtered, there are some time-pressed members of the news profession who might be tempted to grab them for repurposing on some blog. Or for marketing and distributing through a wire service, as Agence France-Presse did with some iconic photos of the Haiti earthquake taken by professional photographer Daniel Morel and uploaded to Twitter with the third-party client TwitPic.

AFP argued in court that Morel gave them license to use his photos by uploading them to Twitter.

Nope, says a judge in New York's Southern District, TwitPic and Twitter's terms of use protect copyrighted photos from greedy wire services.

"AFP's position was a stretch, and it's nice to have some clarity that uploading content into the Twitter ecosystem does not grant third parties a license to use that content outside the ecosystem," writes tech attorney Venkat Balasubramani. Subtext: Take your own photos, AFP—isn't that like, your job?

If you post photos to Twitter and don't want them repurposed, check the terms of service of the photo-posting app you use. A cursory, non-legalistic look shows Foursquare seems to prohibit all content from being reused; Instagram initially used stock legal language that gave away photographers' rights, but changed its terms after Instagrammers complained.