[Ditto]

That picture has been shared millions of times on Facebook without a peep from those who own it. But Sarah Palin does the same thing, and they slap her with a federal lawsuit.

If Palin can show that it has been used many times without permission by the copyright owner, then the copyright owner can not enforce his rights to the image. It becomes 'public domain.'

When claiming a copyright, the onus is on the owner of that right to enforce his right. That is why you see Disney go after pre-schools that use images of Mickey Mouse without permission even if they are making no money on the image. If Disney allowed them to use it without permission, Disney could lose their rights to Mickey Mouse.

[Windflier]

According to posters upthread, Getty has a web crawler that scans cyberspace to find unauthorized usage of their images. When they do, a letter is sent to the user.

They appear to be protecting their copyrights.

[itsahoot]

When claiming a copyright, the onus is on the owner of that right to enforce his right.

Garth Brooks apparently has the letter "G" copyrighted according to Glenn Beck, who also used the letter "G" as his logo and had to change it, because Brooks fought it out in court every time someone used it.