Can the Bitcoin network be used for cracking? I'm assuming that the Bitcoin economy is rapidly building a computing cluster capable of unprecedented amount of hash searching.

Would it be possible for an attacker to leverage this to crack other systems?

E.g. could an attacker input password hashes into transactions and then deduce useful information from the output of miners with regards to hose hashes?

(I'm not asking about the security of Bitcoin as such, so I don't think it's a duplicate of [1] or [2]) 

[1] Could mining calculations be used to crack private key?

[2] How long would it take a large computer to crack a private key?
Short answer: no.

Long answer:


Blocks are exactly 80 bytes long. When have you ever seen an 80 character password?
Blocks start with a bunch of null bytes in the version field. Again, when have you seen that in a password?
Each miner is mining a different block. You don't know the merkle root of what they're mining because that contains a hash of a secret address.
Bitcoin uses SHA256(SHA256(x)) as a hash function, which is not very common in password hashing.
Miners won't publish their results unless they solve a block. They only solve a block if it starts with 12 zeros (at time of writing). The odds of your hash starting with 12 zeros is 0.000000000000003034%.