Labcoin's statistics are visible at http://www.btcguild.com/index.php?page=rankings§ion=teams where their hashrate hasnt increased in 3 days. Some pumper (probably Ytterbium himself) is using his or her accounts at other mining sites and redirecting funds to labcoin's wallet. Labcoin does not have "hidden accounts", it has one account which is visible at the above link.
I certainly wish I had 400Gh/s
And the payments are not from other sites, they're from BTCGuild. They're all paid at the 7, 17 or 47 minute mark, and I'm sure they all trace back to BTCGuild's 14cZMQk89mRYQkDEj8Rn25AnGoBi5H6uer address.