Quote from: a.denis1 on June 18, 2013, 07:54:50 PM

It care if the result of the copmputation is useful because this is the difference from bitcoins and gold I can use the gold also for its intrinsic value ( building electronic circuits etc...) I can not use the result of the computation of bitcoins except as coins

...which is a good thing in my opinion, as you have no other incentives (or disincentives!) to mine bitcoins than to use them. Otherwise you might have additional incentives that might not be related to Bitcoin at all.

Quote from: bluemeanie1 on June 18, 2013, 07:24:27 PM

Some projects pay for computation, why don't people game those systems?

Which? Links? I don't know of any project where you can earn even remotely as much as Bitcoin and only a few peojects (most which probably mine Bitcoins and pay out a small amount of the earnings) that pay anything.