Well, what most people do is speak to Akamai et al and get a decent managed virtual delivery network overlaid on the internet.
But you need to have hundreds of thousands of players, or tens of thousands of subscribers, before its worth the cost of such things. Its not something you should be worrying about now :).
But SGS provides a chat system within SGS on the communication tier, why not use it, if it is already there and managed on mixed client/server and peer-to-peer level?- I never was a friend of extern applications to do ingame chat - neither by voice (teamspeak for example) nor by text using IRC channels. The pure handling of those separate applications kills immersiveness IMO or did you think of a chat system integrated nicely into the client which is just not part of the SGS?- There you would also have to check for people allowed to join channels and such, so you will need some kind of interaction with the SGS too - so I see no real advantage for this approach instead of using the SGS chat system directly.
Ragosch
I think the chat question very much depends on what your are trying to do with the chat and what the costs in time/complexity/management are for each approach. Its soemthing each game will likely decide for itself.