[jeremydavid]

I think you may be mistaken.

These guys were acquired by Google "after a rejection from YC".

http://news.ycombinator.com/item?id=1940386

[jw84]

Google didn't buy a diabetes management app.

[vietor]

By that logic not every successful YC startup was accepted by YC, given the existence of teams that changed their product during their time at YC. Changing direction and refining the idea are a core part of doing a startup.