I know I sound stupid and I know relatively little about the structure of the chip, but from everything i read so far about single threaded design of BD, I'm gonna go ahead and throw a conspiracy theory out there:

AMD is hiding a key feature of BD for single threaded performance: It will be capable of some form of Reverse Hyperthreading.

AMD is hiding this though.. but you heard it here first!
Or maybe I should not post after a few beers.