In my small corner of numerical computing, pretty much every name I know on the east coast who doesn't hold a university position has moved to Yahoo Research in recent years. So at least their research lab does not seem to experience a brain drain.
They had a huge brain drain of their research lab like 4 years ago after some past company turmoil. Andrei Broder and dozens of other researchers left.
They might be building it up again, but I feel it's unfortunate for those being hired, because research is usually one of the first things to get cut when a company is in financial difficulty. Research is long term, and Yahoo doesn't appear to have a long term plan unfortunately.