The most obvious example of this is any visual designer trying to get work for one of the Hollywood majors. A common part of the deal is that, by signing up, the studio now has the rights to whatever was in your presentation portfolio that you showed them. This is not some new development, places like Disney have done this for ages. In fact, Sony Pictures just got outed for doing it when they recently posted for storyboard artists and visual development artists on their own site. Many even put in the addendum that anything you create in your spare time while in their employ is theirs as well (and it's not just entertainment media that does this. The Red Cross has a stipulation that they own any journal writings and such you do just in case you decide to make a book or movie. The Red Cross is low, but I didn't know they were THAT low).
In the 80's, Marvel Comics created an imprint called Epic. It was home for creator-owned comics and had some astonishing stuff come out. Yeah, you had weak shit like The Trouble With Girls, but you also got Marshall Law, Groo, and The One. The whole selling point was it was CREATOR OWNED. Marvel held no rights, they were allowed to print this stuff. Marvel owned NOTHING.
Everybody still with me so far? That's good!
So, Marvel was bought by Disney a couple of years ago. And someone has been going through their records. Mike Kaluta and Elaine Lee created an Epic comic called Starstruck. After Epic folded, they took the title to Dark Horse and to IDW.
The other day, Elaine Lee got a Cease And Desist letter from Disney, saying that Starstruck was Marvel property.
Lee and Kaluta dug through their records (remember, this was the 80's, before electronic filing) and dug up their proof of ownership, the Marvel deal, everything. Conventional wisdom says that it was someone just looking to make a splash with their bosses in legal.
But remember, watch those terms and conditions.
Get a lawyer to read anything you might sign.
Keep organized files.
And spread the word about these tactics.
We must watch out for each other.