This is what #[5] and I have been discussing. Reputation. It's a feature. #[4]
Discussion
I just hope it doesn't turn out like email where you cannot use your personal domain without ending in a blocklist.
IMO domains (without subdomains) that NIP-05 verify only 1 account should be considered trustworthy.
Maybe some free TLD might be discarded, but `.com`s and `.org`s should be good.
We are implementing premium accounts that are subdomains partially for this reason. The other reason is that some clients display username@domain.tld and others display @domain.tld even though both were registered with a username and not (-). 1 subdomain per user may fix that.
Question is what could be the parameters to gauge the reputation of a NIP05 verification domain? More trusted users or less spam from those verified users?
* Usage heuristics (spam %, report %)
* TLD reputation (some are free, some expensive)
* How many users are NIP verified in that domain?
* Is it a base domain or does it have a bunch of subdomains?
Makes sense!
I believe finding that sweet spot will be key.
Do they provide ID to anyone? Do they require any sort of external verification? Is it a premium price? There are many factors that the community will come to value over others. The market will decide these as time goes on and more competition enters the space.
exactly, and different people will value different things. A student might want to verify as @harvard.edu as a status symbol. A doctor might want to verify with the AMA. The possibilities are endless
Absolutely. You get it. Bullseye. 
I agree, those are some valuable parameters to start with.