I agree that voice support is a bit of a double edged sword, but I agree that it must be possible to filter it. Also, in some games, surely it'd be possible to hear those near to you, so you don't hear some bloke five miles away. Also, if someone was boring / moronic / talking about politics in a game (the horror, the horror) you could just walk away, like in real life.
Now, I know you're gonna say "radios were invented ages ago, all soldiers should have one". That's a good point - but imagine a 200 player server with voice support - it'd be like being trapped in a conference call with 12 year olds.
What might also be a good point is that some games may do this already - I am a bit of a n00b in multiplayer terms, but this occured to me during a game of Joint Ops.
_____________________________
Insert funny quote here