This assumes that all Beeper Mini users are spam, and that's a weird take.
More charitably, perhaps you are saying spam will increase over previous levels. From what I understand, Apple does not have any spam prevention technologies in Messages at all, neither for incoming iMessages, nor for SMS messages-- so the only thing keeping your iMessage conversations free of them is the obscurity of the protocol. Perhaps they should just add anti-spam tech like other texting clients have had for years.
When you get an iMessage from a new contact, there's a "report junk" option; I'm assuming Apple does some kind of spam detection with that (ie if a particular Apple ID gets enough reports, it gets blocked). I've never seen any public documentation of it though.
The same technology Beeper Mini uses to get onto iCloud can also be used by spammers, crooks, etc. to get onto iCloud. You either get both or none. Frankly, as a paying Apple customer, I want them to close this because I hate SPAM. Also, the obsession of iMessage seems very strange to me.
More charitably, perhaps you are saying spam will increase over previous levels. From what I understand, Apple does not have any spam prevention technologies in Messages at all, neither for incoming iMessages, nor for SMS messages-- so the only thing keeping your iMessage conversations free of them is the obscurity of the protocol. Perhaps they should just add anti-spam tech like other texting clients have had for years.