I got buzzed by one of these going well over 30km/hr on the MUP in Ottawa (I was going 30km/hr, he blew by me like I was barely moving). While I do understand that it's technically a more green form of single person transportation, and the one I saw was an electric scooter... It does not belong in bicycle lanes or on bike paths.
In particular the MUP's in the area have a 20km speed limit - yes, I was 10 over, but I drop in speed whenever I start to approach other users of the path, and quite frankly my average speed is around 18km and I like to coast a lot. Going 30km is a rarity.

Zooming along at twice the posted limit on a near-silent motorized machine in an area designated for (and populated with) cyclists, roller-bladers, pedestrians, senior citizens with walkers, etc. is the same as taking a motorcycle down these paths IMHO. I have seen the occasional gas powered scooter on these paths too and that just offends me beyond words when I have to deal with motorized-noisy-smelly-traffic on a path I was taking to avoid riding along with just that.

At the same time, those vehicles are nearly as easy to steal as a bicycle so I can understand the owner's desire to lock it up somewhere. Perhaps you might luck out and find bike thieves target the more valuable scooters instead of the bicycles in the rack.