This is pretty much what Delta just did to us. Don't sit up front on a flight? You gotta pay the $50 Delta fee now as of June 23rd. If your hire date was June 24th and you need to get to work on the 23rd? You're paying $100 since it's due on your anniversary date. I know they're doing it to all the DCI regionals, but it's still crappy to essentially charge for jumpseat privileges. If I'm non-reving, cool. I understand paying the fee, but if I walk up, fill out a JS form, get a seat in the back and the gate agent says "That'll be $50," that's BS.
If United starts to do this, expect to see their reciprocal jumpseat agreements start to dry up.