I have never used gmail chat. Well, that's a lie - someone tried using it at me once, but, I just switched it off. It's always been there as part of gmail, along with those too-clever ads which know slightly too much about you (last year's winner: "Is he cheating on you?").
Suddenly, however, gmail's got strangely aggressive. Next to every email I get from anyone on gmail, it informs me, tartly that X "is not available to chat". As though you had your chance, you blew it, and don't you try jumping on the bandwagon now.