I've had quite a few old ICs damaged by that foam deterioration. Once it starts crumbling, it adheres to the pins and seems to have a corrosive effect over time; I've seen some pins partially eaten away. I'm trying to find a way to remove the old foam residue without causing electrostatic damage to the chips, possibly with a mild solvent and ground strapping. Some of my chips are still useful as experimenter parts; but, left alone, they will eventually be ruined.
BTW, the more recent types of conductive foam don't degrade this way. For smaller ICs, they're best kept in their plastic tubes, if available, and avoid using any foam altogether.