The archives here from the old days are full of sayings like 'if you cannot regulate yourselves, you will be regulated upon'. Given the human condition, the later will usually prevail.
The idea of a MAB, motor assisted bicycle, is a great concept, affording a cyclist up to 2 HP (1500 watts) of assist in a majority of jurisdictions. A small, efficient, quiet, unobtrusive power source added to a lightweight bicycle frame is a gift in added efficiency. It can be made to adapt to be within the design parameters of the original bicycle and to inhibit as little as possible the original functionality of that bicycle. It's a sweet idea but only if a certain restraint is used, IE: keep it light, original and looking as much like a bicycle as possible and leave it at that.
Problems are instigated regulation wise when mission creep sets in to turn MABs into fake motorcycles, a not so thinly veiled attempt to build a cheap contrivance of dubious build quality that skirts the law, license fees, liability and regulation of a whole vehicle class. Some of the "cry freedom" types can yammer all they want but no one is fooled if they're just posers and they want it both ways: they really want a motorcycle but they think they're fooling everyone by being cheap and shirking the responsibility of owning one.