Something tells me you'd probably have a very different opinion if one of the cofounders from a venture YCombinator started disappeared only to resurface later with VC-backing and a "I don't owe anybody anything, I didn't sign any contracts, it was just as much my idea as it was theirs" type of attitude -- especially if that guy went on to use his capital to start what would go on to become a very successful company while the one you founded floundered into eventual obscurity.
I mean this in all honesty when I say I hope it never happens to you guys like that, but something tells me if it did you'd be writing an article proclaiming something to the effect of, "That's Bulls@#$!!! People should respect other people's hard work!"
In conclusion all I'm really saying is "proceed, but with caution" since in the end there are a lot of VCs who'll more than readily copy your idea and give it to a friend or two they'll fund to "execute" your startup on their terms and not care twice about the bad reputations they develop as long as they make enough $$$.
And apparently by one of the most recent postings on this board, ie, "An Engineers View of VCs" or something to that effect, I'm not alone in this impression: