Interesting, the system throws random answers (returned shares) at a problem and people attribute long solves to "luck" rather than just the normal probability distribution of solving a block.

If I jumped to a new pool that found the block as soon as I joined, I might get 0 shares out of 100, because the pool was "lucky" to find it right then, but my 100000 shares in the previous pool will contribute to the next block found there anyway.

Willing to be proved wrong, someone might want to supply a link that shows, over a period of a month or longer, for 1000Mhash mining (ie, non trivial) the average return from sitting versus hopping?