Ask HN: Is a distributed computing cryptocurrency possible?

Essentially, applying the philosophy of REcaptcha to cryptocurrency.

SETI@coin, FOLDING@coin, etc..

Is this a viable way to mine a cryptocurrency? Has this been implemented before? Are computation results verifiable?

In a similar way, could companies could issue the crypto equivalent of private notes/bonds by buying what is essentially (ethical) botnet use from users and issuing a currency for computation results?

My guess is that issues would include decentralization (lack thereof) and verification of results.