I'm all for speed limit rather than class limit, though I'd like to see 20 mph posted as the limit in a relatively empty bike path. In a shared bike/walking path even 15mph seems high. Common sense dictates slowing down in a crowded area but there are those that would still go 15 mph.
$100 seems a little steep for no tolerance. It can be made up in other citations. In the big apple, I've seen tickets given out for violations of stop signs, riding in opposite direction of a bike lane, and riding with both ears covered by headphones or ear plugs. These were all in Manhattan. Don't think they were at $100 a pop, more like $25 and $50. I feel people would respect those lower fines when pertaining to just a bicycle.