I can think of 4 products I have with rubberized plastic surfaces on them that have degraded over time. (IKEA scissors and kitchen knife, Logitech wireless mouse, Rocketfish wireless keyboard.)
The rubberized surface has become gooey and sticky after years of (minimal) use, to the point where it leaves visible residue on my skin or I leave fingerprints in it. The back of the keyboard became sticky like glue.
At first I thought it was just one product and the factory screwed up the plasticizer mix, etc. But now that it's happened in multiple products from multiple companies, is there something in my environment that could be making this happen? Humidity? Sunlight? (I don't think the mouse or keyboard were in the sun much.) A chemical in the air?