So if the problem with lists is that they require effort to maintain them, how about lists with algorithmic maintenance suggestions? People that are hands-off can leave it fully automatic, whereas others could still make use of suggestions to maintain their fine-tuned lists more easily.
Still requires effort to maintain. You have to click to add friends. Take a page from Facebook. It's now really hard to manage lists; they encourage you to use automatically-generated lists, though. I'm sure they had reams of data to support this (over the objections of vocal power users).
