If it can be gamed, it will be gamed 😂 
Discussion
1000 sats is the threshold
New client-end locally run algos based on follows, follows' follows (following degrees of separation, FDoS), etc. are needed. No one's going to follow speak accounts, so they'll only be in direct contact, just ignored for those with FDoS 2+.
"Trending" can't be global. It just won't work long term for the reason you just put forth. "Trending" needs to be FDoS 4-, maybe even inversely scaled somehow for the FDoS.
*No one's going to follow [spam] accounts
Except for spammers, obviously. An FDoS2+ account may be ignored/pruned if the follow list is too great (1k+ reduced weight, 10k+ fully pruned), since those won't be authentic follows.
Mutual follows get greater weight with some diminishing returns. This will prioritize your interests, or rather that of those you follow.
The social graph could be mapped client-end in a cache for FDoS <5, ignoring lists of greater than 10k, and stopping at lists of 1k**.
Hourly, trending for FDoS 2
Daily, trending for FDoS 3
Weekly, trending for FDoS 4
Biweekly, trending for FDoS 5
**(You follow B, B follows C¹ & C² & C³ & ... & C¹⁰⁰¹, don't look through Cⁿ's follows)
“You wouldn’t download a car”
Like fuck I wouldn’t 😂 I just couldn’t at the time because the technology wasn’t available
If it can be hacked, it will be hacked 😆