Bubbles have to have widespread macro-economic build up that will indicate whether or not there is actually a bubble. Are IPO filings up? Is the average dollar amount raised in Series A significantly higher? Are there more visible failures than before? Unless you can scientifically point to some data or experience that MANY unqualified startups are in fact receiving easy money, than you're just a speculator. Because while YC companies have a large attention-share in the startup world, it is still only a fraction of startups and non-representative of the larger landscape.

I hate it when people ignorantly say things like "this is a bubble" just because they read about some dumb company received funding in a TechCrunch article. (Not a personal attack btw on you btw, just my general opinion.)