In California, I believe it is illegal for pedestrians to be in the bike lane on the road, unless, they are on a road that does not have sidewalks. I looked this up awhile back because I was so frustrated with joggers in the bike lane. I think the main reason they do it is because they think asphalt is better than concrete for their knees... I think that the sidewalk is often better than the pothole-filled street for my carbon fiber bike and for my aging joints - but I don't go riding on the sidewalk for this reason...
I think it is suicidal for anyone to be walking or jogging in the bike lane. There are tons of strong roadies on aero bikes in the SF bay area that can easily ride 25mph on flats and 50mph+ on downhills. In my mind, walking or jogging in the bike lane is not much safer than walking or jogging in the lane of car traffic. I wouldn't do it, even if someone paid me. I also think that all these years of signage telling pedestrians that everyone in the world must yield to them at all times has created an unsafe, entitlement mentality. I have seen moms running with headphones on while pushing strollers on the MUP with one or two dogs attached, on retractible leashes... How do you safely get around that? I think there should be a yellow line painted in the middle of all MUPs with signage telling all users to stay to the right. And there should be occasional enforcement of this, just like how it works on the road with cars. I think cyclists need to start being more assertive about their rights - especially in regard to MUP's and fire roads (for mountain bikers).