Suggestion to Ello:
Do not allow following or unfollowing more than 30 - 50 people per day.
If it was up to me, I'd make 10 the limit.
Organic followers and interaction > (a)social media marketing tricks
EDIT: Take in mind this was an issue that Twitter already had to deal with. The way they handled it was not allowing following more than [the number of followers + 2000], but I think that still leaves space for trickery especially with the help of follow-bots.