If you're able to gather this data in a way that the user doesn't notice it, I've got another idea:
Would it be possible to compare your own follower list to the follower list of another user in the moment you have to decide wheter a boost is helpful at all?
Background:
Sometimes I see the same note boostet again and again and get the feeling that half of these boosts are sent to >90% of the same followers.
Clients could prevent showing the same note boosted again and again within maybe 10 minutes, but that would be just another first aid kit...
