Finally, I have been growing concerned for some time now about attempts to defraud pools. The pool's luck has been on a decline for over a year. The luck on a few other pools has also shown a negative trend. While it is not impossible that it's a coincidence, this is something I have been constantly made aware of and am helpless against. There is no way to know whether it's just bad luck, a small bug in older miners (BTC Guild probably has the highest percentage of first/second generation ASICs) resulting in a few % of block-solving shares to disappear, or a large pool trying to hurt the competition (many of the largest pools have large private mining operations now). It would only take a fraction (1 PH/s or less could do it) to cause significant harm to a competing pool, and that activity could be masked by proxies and multiple accounts to be impossible to catch.