It's all fun and games until a picture makes big bucks. Then, you'll see lawsuits; I didn't read the user agreement well, didn't understand it, it's unfair, it violates [insert law of any US state]...and so on.

Have you seen that CNN and the likes make it absolutely clear the intention when they seek pictures or video for live events (earthquakes of example)? Not hide it on what would page 83 of an agreement.