Sounds like a micropayment system where there is much more significant first buy in amount to be on the micropayment system than the actual (tiny) cost of a micropayment to use a service would make it worth far less worth it to spam online services.

The risk of having their payment identifier/address banned from services before significant use makes it very risky for them to use such a thing even if tiny micropayments a worth it to the spammer.

It certainly could have other problems with people getting banned from such a system for things other than: spam and other use detrimental to the service provider. There is also the issue of how the initial buy in fee is distributed.

But a high buy in for a system that many online service providers use would very strongly discourage use detrimental to the services providers (I think; this is only for discussion, as this is posted by someone with little knowledge on this. Micropayment systems have been talked about a lot, but I don't remember high buy-in mentioned).

Edit: Forgot to mention that the idea of this is that service providers can offer their services at lower cost because the risk to them from a account/address with a high buy in is lower than from an account/address with no buy in.