The best part of the fediverse is that anyone can run their own server. The downside of this is that anyone can easily create hordes of fake accounts, as I will now demonstrate.
Fighting fake accounts is hard and most implementations do not currently have an effective way of filtering out fake accounts. I’m sure that the developers will step in if this becomes a bigger problem. Until then, remember that votes are just a number.
No need to make all federation under a whitelist. It’s enough to ignore votes from suspicious instances or reduce their weight.
Depends if the rate of creation of the suspicious instances is higher than the mods can manage.
New instances would have a lower voting weight by default.