Now you're screwed, I hate it when that happens! We've been known to
use a variety of homemade tools to remove those, there's not really a
tool you can buy that will just 'pull it out'. Various combinations of
lump hammers, bars, washers, sockets, bearing pullers, chisels and
anything else that might do the job are what you need!

Tried most of those, though a socket ... good idea ...

On the subject of bearing pullers, and cant see how it works ...

http://www.tooled-up.com/Product.asp?PID=13663

Surely the central bit needs to push against something when its screwed
up/down to pull the bearing out ?