I ask this question in all sincerity, but it seems to me that the answer can only be
Kovid Goyal.
At last count, his
libprs500 tool has been used by two different e-book vendors (Fictionwise, and Baen) to make their offerings available in LRF format. Seems to me that he's been more successful in getting the BBeB format out there in just over a year than
Sony has in the several since they came up with the thing.
I think even for folks who don't use the application, that's worth noting, and perhaps a word of thanks. For those so inclined, note that he has a tip jar up on his site.
Also note that Kovid has no idea I'm posting this, it's all my own thoughts and idea. I know I'm running the risk of embarrassing the poor guy, but I thought his achievement ought to be specifically pointed out and recognized.
So thanks, Kovid, you rock!