[ear1grey]

The use of separate keys is important for several reasons, firstly, you’re not just using the Akismet database, you’re contributing to it with every message you send. Each time Akismet makes an assessment and you don’t disagree with that assessment, you’re contributing. Being able to remove contributions from bad people once they’re identified is a useful ability, if everyone used the same key this would be more difficult.

Obviously bad people very much want to be able to affect the DB so that their spam can get through.

So when bad people are spotted, they must be stopped. The key helps here too because (I recall from looking at the original plugin source) it becomes part of the connection URL, so it’s possible if necessary, to block connections to that URL at the firewall level, so the servers can concentrate on fulfilling requests from good guys.

A single hidden key would be very quickly compromised, and would thus be very quickly disabled, and you’d be back to needing your own key.