Elaborating, he said "the longer you play a character, the more bit differences on objects (characters, pencils on tables, containers, etc.) get saved off and carried around in memory, I think we've seen save games that are pushing 19 megs, which can be really crippling in some areas."
One user asked if the problems are exclusive to the PS3, to which Sawyer answered "as with Fallout 3 and Skyrim, the problems are most pronounced on the PS3 because the PS3 has a divided memory pool. The Xbox 360 has a unified memory pool: 512 megs of RAM usable as system memory or graphics memory. The PS3 has a divided memory pool: 256 megs for system, 256 for graphics. It's the same total amount of memory, but not as flexible for a developer to make use of."
Source: Bethesda