Your comment is funny but true. People will always find rational reasons to explain away sky high valuations. Even the first time around, Pets.com had a very high market potential if it capitalized successfully on projected internal sales growth rates and expanded to the size of the pet care market.

I take all these comments very very lightly. In my experience, the surest sign of a bubble is when the non-savvy bench investors in your life start talking about "great investment opportunities". When 9/10 people in your office are buying a house as an investment opportunity, there is probably a bubble. When 9/10 of your office is investing in the secondary facebook market (or something similar) chances are there is a bubble.