I don't really like the idea of throwing data away because it ultimately gives an incomplete view of the system. But, easy solution to solve a hard problem!
Sampling is fundamental to so much of practical statistics. It's more or less proven and accepted. In real studies, we "throw data away" by just not collecting it in the first place. As long as you do it right, you still get a reliable answer.
But if you've already got it all and it all fits in memory, by all means, hold on to it!
