Right now the stock is in an uptrend. There are certain institutions and large investors that actually look at this as a technical buy signal. Read Investors Business Daily for more info on this "buy high, sell higher" philosophy.
Then you also have day traders and individual investors who believe that, if someone just paid 171 bucks for a stock that was 150 a few days ago, then maybe someone else will pay 190 for it in a few more days. This is where the 'greater fool' theory comes in.
Believe me, IBD is recommending purchase of this stock, and I am sure that it is being discussed in the Board rooms of many large investment and Mutual Fund companies.
Thanks for that---it's what I would have guessed you meant, but wanted to be sure. As a relative newbie, it shocks me that such basic tenets of investing - SELL high and buy LOW and DD on valuations can be disregarded in favor of chasing the trend of the moment.