I noticed this while IM'ing with a friend of mine - Brink seems to go nuts while I'm tabbed out, allocating an extra 10-12MB a second of memory, until it runs out and crashes. It seems pretty consistent. Tabbing back in again does drop the memory usage back to normal levels, but it can take several seconds for the game to respond (I imagine it's cleaning up the huge heaps of excess allocated memory during that time).

Not a priority issue, obviously, but probably should be fixed. In the meantime, don't tab out for too long