[Cryptography] How secure are hashed passwords?

[John R. Levine]

I see in the press that eBay had a large security breach, in which the
bad guys stole a lot of personal information such as physical address
and birth date, and the encrypted passwords.  So eBay wants everyone
to change their passwords.  Huh?

Assuming a reasonably competent implementation of password hashing
(which I realize is a leap of faith here), with a strong hash and a
large enough salt to make rainbow tables impractical, how much can the
bad guys recover from the hashes?

R's,
John