Brute forcing passwords is a very bad way to get a password. It takes alot of time to do that. Days , weeks, months, years even !
That's why it's never used, i wouldn't worry about it.
But what if you have great amount of hash power like Chinese mining farms?
they could become rent services when mining becomes unprofitable.
The hash used by Bitcoin is SHA256d, which is not used for anything else really. ASICs wouldn't be useful for breaking hashes because they can only do SHA256d.