I think it's a bit shortsighted to assume that everyone who has a problem with this sort of behavior is riding the MUP like it's a race. When I'm going under 15mph and my 3 or 4 shouts of "on your left!" fall on deaf ears, it's bloody inconsiderate. Not to mention dangerous. It is not too much to ask to have people keep to their lane. The MUP has lines and stop signs just like the street does. I don't understand why people feel the need to walk 4 or 5 abreast or in the lane of opposing traffic. Why not walk in rows two abreast for cripe's sake?
Oh, and dogs? I've had people look back directly at me, make eye contact, and STILL not reel in their dogs. I whacked the hell out of my knee on my handlebar a few weeks ago having to make an emergency stop to avoid a dog. Even an accident at 10mph can have nasty consequences. Could have been much worse just because somebody wasn't paying attention.
I swear, I'm going to mow over somebody's kid one of these days. When you shout out "on your left" to a five year old they don't know what to do, they swerve wildly. I go very, very slowly when around small children, but the ridiculous part is the parent walking twenty yards behind yapping on his or her cellphone not paying attention. I hope for the child's sake that they don't get hit by a car at an intersection because Chatty Cathy isn't paying attention to where her child is or what he's doing.
These aren't things that happen too often, but it only takes one incident to ruin your day and theirs.