After a certain number of suggestions it's a bad system that only helps follow spammers. What I mean is, once you're getting towards three degrees of separation there isn't necessarily a lot you have in common with that person. I find that it's useful for discovering some interesting accounts, but after a while the suggestions are dominated by celebrities and big brands which nearly everyone follows, but the people in your interest group aren't necessarily any more likely to be following them than the general population is, (or the general population of your country, at the least).
Twitter could do a lot to refine this tool. Perhaps they should also consider throttling it for people who are already following more than a thousand accounts.
I don't think it's perfect or that it's terrible. It's pretty apparent to me that it keys on the context activity sphere of people you follow, the 'air bubble' gap accounts that are active in that sphere but that you don't follow. They'll pop a promoted account in there now to further impress on you someone's account who's willing to pay to have you follow them.
I would assume it's a similar theory to the facility that Facebook has.
Their suggestion system has a LOT of fundamental issues
I doubt it's as bad as that, maybe it's just not as complex as people assume. Without looking at the algorithm, we don't know, but I would assume the reason why the same people keep on popping up is because those people still match the criteria, and have not been followed yet. I would have thought there would be a random element involved, but then again, there may not be.
I wonder whether Twitter doesn't make it more advanced because they assume you will follow people based on the real world, rather than Twitter itself. I dunno though.