It appears that over the weekend a search update that affected the search results began taking place. A WebmasterWorld has a thread where folks are discussing the changes.
Senior Member steveb said yesterday;
Still at least two main indexes... the apparently being replaced that had tons of freehost spam, and the newer on with much less freehost spam but different data-refresh/lost/screwed-up sites.
Where are people noticing the changes? One member documents the data centers.