Can brokerage firms do this?

Suggest you are a large brokerage firm with millions of accounts, wouldn't it be easy to employ the following winning strategy:

1) among all customer accounts, find 0.1% most successfull
2) copy their moves exactly

good idea
Well ,that's something i have also thought about.
I think Darvas mentions in his first book that he spread his trades among several brokers. However he also mentions in his last book, that one of his brokers does not believe in his methods and things he acts on insider information. Gary Smith however had just one commdities broker till 1996 or 1997 for more than a decade, and says that sometimes ,when he said buy instead of sell, the broker used to correct him, because the broker knew exactly how Gary traded..
Different people, different opinions.. Some people would never even touch a stock at a 52 week high, others might think it's too high and short it, and the rest might think of that stock as a "bargain".
If i were a broker though, i would most certainly follow those customers with steep and uptrending equity lines. Or as Marty Schwartz said to his runner on the Merc -look for the winners on the floor