Trikes and ... other more than two wheel thingies, seem to be very popular this year. I saw a number of these three wheel Can Am things. They sort of resemble a snow mobile and I suspect they may have a snow mobile in their Can Am heritage.
I saw a lot of Sportsters with four wheels in a training wheel type configuration. Several had trailer hitches, and several appeared to be removable. I guess if you are feeling tippy you bolt on the other two wheels for security. While I like a nice side hack and would have one if I had the room, I think trikes and these other three and four wheelers are just weird, but to each his own.