As nice as interoperability (and the accompanying possibility of something like a modern-day Adium) is, I worry that this will introduce SMS' rampant spam probl

As nice as interoperability (and the accompanying possibility of something like a modern-day Adium) is, I worry that this will introduce SMS' rampant spam problems to iMessage and the various other messaging services that will also be required to open up. Part of the reason spam is so rare on iMessage is because it requires an iCloud account on an Apple device, which not only raises the barrier to entry significantly but also means that spammers are easily dealt with via account and device serial bans.