The "locks" around the edge (at least, I think that's what they are?) would never show up clearly if the image gets much smaller.

The coloring is pretty, but a bit.. "much".

The "current" logo:

http://utopianist.com/wp-content/uploads/2011/05/bitcoin-online-p2p-currency.jpg

Is simple, it's not confusing (the "dollar sign" marks in the B itself lend itself to be viewed as a monetary unit), and... well, it works.