Nothing. I have often run in the actual lane of vehicle traffic where there's no shoulder. I just don't see what's such a big deal about this. If the runner doesn't hop up on to the sidewalk, then just go around them like any other obstruction in the bike lane.

You sound like so many impatient drivers. Sometimes I run around the track. Often I run from my office to my house (run-commuting, if you will) because I'm a working dad who's always looking for ways to maximize my limited time for fitness. I would be thrilled if the city laid out a crushed granite running path from downtown to my neighborhood, but since the likelihood of that is zero, I'll use city streets for now.