I'm sorry, do you not agree that the USA has a "compensation culture"?  Certainly that is the view of the world media.  And certainly that "compensation culture" is slowly invading Britain as seen in some prominent news stories over here at the moment.

At a time where photographers have to be ever more vigilant, it would make sense to obtain a model release if you can if the shots are going to be sold as non-editorial stock.

I enter the contests when there is one that fits my shooting style and available models/props.  I'm not that concerned at this point with having to leave it for a year.  I don't expect to be leaving DT

Can't say it has had a direct impact on my income via huge sales of the contest images, but it does up your exposure IMHO.   I get the impression buyers keep an eye on the contests, and if you upload something they like they may take the time to check your other work. 

I think that is the best course to take.  The images which get accepted appear on the front page, at least until newer accepted images drive it off.  So I agree you do get a lot more exposure.

When I got the editor's choice image in early March, not only did the image itself sell multiple times the first week, but my overall sales spiked.  If you can get extra exposure at Dreamstime, it's definitely a good thing because volume is respectable, and commissions are very fair.