Do they really think us few crackpots mining Bitcoin would be even a dent in the AMD total sales?
Depends on how do you define "a dent". The Bitcoin hashrate increased by about 1000 6990 during the last 3 months. It's about 0.1% of the AMD graphic revenue during a quarter which is around $400 million.
Of course not all of the new mining capacity went to AMD (some were old purchases, or nVidias or ArtForz's ASICs) but all 6xxx purchases and a large part of 5xxx went directly to AMD.
If the difficulty increases 10-fold, which is highly likely, the increased capacity will be 1% of the AMD GPU quarterly sales. It will start to be a non-trivial part of their market.
