It's a natural mistake, given the fact that it's a German name. In Germany the "bocker" pronunciation is correct. Most European languages have very consistent rules of pronunciation, and in fact most other languages don't even contain the american "baaa" sound, thus some non-americans may even struggle to pronounce Rickenbacker the way we do, saying Rickenbecker or Rickenbocker instead.
Native speakers may have never heard it pronounced correctly, so it's up to us to take over, erm, I mean educate the world.
You say tomaytoe, I say let's dance!
