I also don't think electric folders are ideal for multi-mode either, but that seems to be the point.

In a highly urban environment with a good bus/train system, you don't need an assist, esp. when everything you need is only a couple miles away in town. In suburbia (depending on which one of course), an occasional 20mph boost is a boon when you need to be somewhere at a certain time. I'm all for human power, but I see electric assist as valuable when it comes to pulling heavy items such as our pedicab; others have tried it with velomobiles as well. They are also useful if your job requires you to dress well but you don't have a "changing room" at work, which is my wife and sister's case.

I like the BOB trailer idea because it could carry the majority of the battery weight and can be removed. I'm even wondering if it would be possible to install a small solar panel as well to help recharge the battery packs, or is that overkill?

I like the BionX system because it can be recharged while riding, but you have to use its proprietary wheel. I also like the Stokemonkey, but it is expensive and only fits larger-framed bikes. In any case, battery technology seems to be the major limiting factor to making electric assist a viable alternative for many people. That and some people's aversion to sweating.