Because I havent given it any thought, and I already had an account at slush before I discovered bitminer . Since we are talking about like 5  proofs of work per day, I cant be bothered to find and register and configure a better suited failover pool That said, maybe I should, not because of 0.0001 BTC difference, but because slush appears to be down again. Guess I should go and try p2pool.