In an unshocking turn of events. It has been discovered that the PS3 version of Skyrim has a bug. One that exceeds the many other bugs that the game already has. This one makes the game virtually unplayable for some players (not all). Once the save file of Skyrim hits about 6MB there is a chance that the game will suffer major frame rate problems (1-10 FPS) and lag almost everywhere. Apparently this issue has plagued one of Bethesda's previous games: Fallout New Vegas. One bug that was apparently never fixed.
Source: http://www.eurogamer.net/articles/2011-11-16-skyrim-players-call-for-ps3-save-file-bug-fix