Yes, it's a natural result of the plastic having aged. It's really unavoidable, and some figures utilized paint that made the condition worse (I'm thinking here of Clamp Champ, Snout Spout, Roboto, Randor and several of the Horde and Snake-Men figures.) It seems like the worst offenders are the ones that came out towards the end of the line, which may or may not be a coincidence.

Being curious, I just took all my stickies off the shelf to examine them, and 90% of them were manufactured in Mexico. The other 10% were Malaysian. None of the Taiwanese figures seem to be affected.