Because Salmon is an open standard, any service can implement it without formal business relationships, and Google Buzz is expected to enter the Salmon ecosystem next. If a substantial portion of the technical community implements Salmon, Facebook could be under a lot of pressure to do so as well. (As it was with OpenID, for example.) If you could still message your friends inside and outside Facebook, it would be a lot easier for innovative new alternative networks to lure you away from the one big site that 400 million people use today.