customisable limit, which then gives you an in-app notification + shorcut to clear cache

"Compute WoT locally" is the opt-in setting, provider otherwise. Limit won't work because it's an all-or-nothing thing. Partial graphs aren't very useful.

The main issue is that IF nostr succeeds, 2GB will turn into 2TB just for contact lists. So, we can keep computing locally while we can, but at somepoint it will just be impossible to manage locally. It's also true if you want WoT scores for every event (me talking about Nostr should have a higher score than me talking about soccer) instead of just per key. Rotation will only go so far.

Premature optimization. Let's do the thing that we can do while we can do it, not worry about a hypothetical world that has a couple billion nostr users.