Under the current ToS/EULA for the community site that (WotC owning all you post) is not the case. You still own it, you just give WotC the right to use it when and how they want.
Of course, the idea that WotC developers are going to waste their time sifting through the ideas on the forums looking for the one idea to steal as opposed to coming up with their own is, to me, solidly in the realm of Aluminum Foil Deflector Beanies.
Ah, but that's what the internets is for!!! All sorts of tinfoil hats!!!
To claim that WotC's current policy is a hidden "cost" is more than a mite ridiculous! Are people really worried about WotC hovering over their boards just waiting to steal their brilliant ideas!?!?!
I don't do much more than lurk over there anymore. A lot of the long term posters who had really cool ideas to share have vanished, a lot of forums are pretty much dead as far as traffic goes (FR for instance is glacially slow), and that's outside of the fact that at times some of the more extreme fanboys over there have taken the Insider tag to apparently segregate them from the the not-really-true-D&D-fans.
I know why they have to do things the way they do it just isn't the most friendly and relaxed forum for the average gamer to exchange ideas compared to non-corporate affiliated sites. Since there are many places without attached strings to gather and share ideas it doesn't matter if one particular site has more restrictive policies. Gamers can vote with thier bookmarks.
That. There's no way your average gamer who creates stuff for himself and his friends cant risk putting his ideas on WOTC's forum and having it come bite him back in the rear, using his ideas and finding out he doesnt actually own them anymore.
I know more than a few folks like that that dont want to risk what they consider theirs. Even if Wotc never uses them, they dont want to take the chance.
That. There's no way your average gamer who creates stuff for himself and his friends cant risk putting his ideas on WOTC's forum and having it come bite him back in the rear, using his ideas and finding out he doesnt actually own them anymore.
I know more than a few folks like that that dont want to risk what they consider theirs. Even if Wotc never uses them, they dont want to take the chance.