The Five Dumbest Things on Wall Street This Week

Sensitive System UBS trips, and AMD gets a round trip

1. Advanced Micro Gets Micromanaged

In this week's Unfortunate Timing competition, UBS analyst Tom Thornhill is the undisputed champion.

On Monday, Thornhill decided that the recent decline in the stock of chipmaker Advanced Micro Devices (AMD Quote) had landed AMD in the realm of a fair valuation, near his $20 price target.

So Thornhill upgraded the stock from a reduce rating to a neutral. Of course, he pointed out that any significant drop in AMD's flash memory revenue wouldn't be good for the stock.

How right he was.

Later that day, AMD announced that flash memory sales, previously forecast to be flat at worst, were now expected to drop in the fourth quarter, resulting in an operating loss.

AMD shares got hammered Tuesday, plummeting 26% to $14.83. And on Tuesday -- one day after raising his AMD rating from reduce to neutral -- Thornhill cut the rating from neutral to reduce. He cut his price target as well, from $20 to $12. ...