Just think this from a profit standpoint:
If you generated X bitcoin with Y hashing power, would you really want to rent that for anything less than what you'd be getting from selling bitcoins?
If you're buying Y hashing power, would you want to rent it for more than your making from selling X bitcoin?
Exactly, a classic arbitrage model. Although it might be easier to sell 10 or even 100 hours of GPU /CPU time for 1 bitcoin then it would be to mine that coin depending on the complexity and effort involved in mining a single coin.