So we got super lucky on 281626. We found it at the same time as GHash.IO, but theirs got orphaned. The weird thing is, the next block, 281627, was found by GHash.IO. So why did they not used their own 281626 instead of ours?
It's not uncommon for large pools (even slush has done it before) to have multiple bitcoind servers and pool servers. It is actually possible, due to the inefficiencies of p2p transmission, for a pool to orphan its own block. By default bitcoind ignores other blocks that come in if they already have a block at that height, so if one of GHash.io's servers saw slush's blocks before another Ghash.io block, it will build on Slush's block unless they have modified bitcoind to prioritize their own blocks in the event of a race.