I think Bitcoin is going to crash at some point and I am not a very good gambler, I don't have the balls to risk everything on trying to get rich so I'm just staying out of it. I should regret not buying back in early 2011 (when I first saw HN submissions about it) but I know if I had I would have sold as soon as it hit anything close to $20. At least that's what I'm telling myself to make it easier to swallow. Therefore I have bought 0, but I do have 0.05 that someone gifted to me on reddit, which is worth $10 I think.
If the price is being driven by new speculative investment (ie, a bubble), the price should stagnate as fewer speculators join the pool. If the price stagnates, there will be little incentive for purely speculative investors to keep their money in BTC.
The last cynic buying in is just an indicator of late-adopters hitting the market, signaling little gains left to be had.