can you explain your statement? Are you saying that a CPU. or 10 CPU working in a pool will never be able to find a block? or that it would just cost too much?
The effectiveness of your hash rate is relative to everyone else mining. CPU's pale in comparison to GPU's which pale in comparison to ASICs. For CPUs to be viable again, you'd need to see a very significant decrease in overall hash rates.
So you are saying that it effectively a race to get to the next new block?
Something along those lines. I don't quite fully grasp exactly what the miners are doing. I think they are trying to guess the encryption of the next block in the blockchain and the miner that guesses correctly is rewarded 25 BTC. That's why you always see remarks like "(if you're lucky)" when talking about mining.
Anyone else care to take a stab at this explanation? I don't think I did it justice.