After interviewing for PriceAdvance we were concerned that YC would mention our idea to Bountii as it's in a similar vein. They did not, and further demonstrated a level of integrity I imagine is unusual in the VC space by not doing so. (http://news.ycombinator.com/item?id=78761)
Without hearing more about how your idea was different it's very difficult to say whether or not it's just obvious next step, something others would easily come up with. It is, of course, with anything, more about the team than the idea, as has been said elsewhere. The execution rather than just the idea itself.
Regardless, for my part, I find YC above reproach when it comes to any insinuation that any sort of collusion or anything untoward might occur with respect to genuinely interesting / novel / unique ideas.
Without hearing more about how your idea was different it's very difficult to say whether or not it's just obvious next step, something others would easily come up with. It is, of course, with anything, more about the team than the idea, as has been said elsewhere. The execution rather than just the idea itself.
Regardless, for my part, I find YC above reproach when it comes to any insinuation that any sort of collusion or anything untoward might occur with respect to genuinely interesting / novel / unique ideas.