I've done some work in this area - it's disappointing how terribly the Twitter product has failed to evolve to take account of bot usage.

There are (of course) some useful bots, but lots of incredibly harmful bots, they they should be treated differently to actual humans.

But Twitter can't ship product, so it's not really worth suggesting what they should do.

In the mean time, my colleagues and I got a nice WWW18 conference paper about a new unsupervised (!) way of detecting some type of bots on Twitter. Like most things it's completely obvious in retrospect...