Two winters ago they had half a dozen (maybe more) at Epcot, and at least one at all the other parks. They also had them in the public phone areas/lobby areas of the resorts. I believe they've all been removed at this point.
What I noticed when they were still there is how many kids came along and banged on the keyboards. It wasn't just a kid now and then, it was almost every child who passed by. I'm sure they weren't meant to take that kind of abuse. It was pretty bad.
I've wondered if they could have made a removable keyboard cover, something that would slide away once you inserted your credit card to buy some internet time. Hm.........