Given the complete lack of information on this problem from the people at Spotify ("we're working on it" and "try a reinstall" doesn't count as information), I can only assume they have no idea what's going on.
Here's something I found that may help. This is for the Mac version...
No need to reinstall everything. Deleting the sp_people_0.localstorage file will temporally get rid of all of the unwelcome people in your list.
Of course, this is temporary. I did not look at or connect to any public playlists. After playing some song and searching for a few different artists (after maybe half an hour), my people list was repopulated with unknowns.
So.... Not at all a fix, but maybe identifying the file will help. Of course, the problem could also lie elsewhere and this file is just reflecting a larger issue.
PS - I know a handful of customers is a drop in the bucket to your company, but you've got a few days left before I take my business elsewhere and do my best to convince my friends to do the same. As many people have stated already... This is a severe violation of privacy.
