The most popular electric assist bikes I see around here are fat bikes and also fat tire folding bikes with 20 inch wheels and 4 inch wide knobby off road tires. Most people use them for commuting and just getting outside and enjoying the outdoors. I never seen one on singletrack but I do see them regularly along rail trails and MUPS. Personally I don't have a problem with them as long as the riders behave responsibly and don't buzz people.. I like the concept of electric assist bikes but the battery range is way too short to justify buying one. These bikes need to be designed with some kind of integrated charger inside the hub that recharges the battery while riding, similar to a vehicle alternator.