I don't buy or sell stock on anyone's recommendation. However, I do use it as a starting point to do my own DD. In this case, Cramer's "reversal" on YHOO is dramatic, so I think he knows something and he wants to take credit for a "good call" after it pops.
I started building my YHOO position 2 weeks ago. I actually was upset that he recommended since now it may go higher before I have time to accumulate what I want.