Social? The internet?
Im against built in voice chat. The problem with it is this;
When its automatic then you have to listen to everyone, some people you don't want to listen to. The solution is simply to turn it off you say? While thats fine on paper, the fact is that when something like voice chat is available for everyone to use, it becomes expected that everyone use it.
I really think 3rd party programs handling voice chatting is the best. Its the best balance. People who want to use it can, but they have to put the tiniest bit of effort into it. And people who don't want to use it don't have to be shunned for not using it all the time=P
I personally listen to music while playing my games. And im a critically listening audiophile weirdo so i cant have annoying people interrupting my pleasure. Ive got enough hassle having to explain to people in MMOs i play that 90% of the time i wont be joining them on vent because of this, id rather not take heat for it over other games as well ;_;
So, to summarize.
Include it and it becomes a socially accepted requirement
Disclude it and people can use vent/team speak/whatever just as easily.
One of the great things about the internet is that its text based. This lets you do exciting things with your other sense simultaniously, doubling your efficiency! Sometimes i listen to audio books, or old time radio programs

. Sacrificing that just so people can bombard me with low quality audio of their own voice every once in a while instead of just typing is a step backwards.
Again, for my argument to make sense you must understand that i know, from experience, that built-in voice chat more or less sets a standard of everyone using it, thats not theory, its happened before and ive yet to see a case of it not happening.