The only thing I have to add pertains to real-life friends who may not tweet too much, but are certainly boring in what they say. In these cases I usually elect to suffer their occasional inane tweets rather than unfollow them (as I have on at least one occasion been questioned as to why I did so, and chose to lie, citing a Twitter error). Perhaps it's a failing of mine to be unable to be honest with my friends, but it feels unnecessarily cold to outright tell someone that they write boring and trivial tweets when actual harm can result. It's a toss up between brutal self-design and maintaining public relations with those few friends who just don't have anything interesting to say.