No, webcams are not supported in World of Warcraft at the moment. The client has voice chat built in (although it is not really good), and text chat but that is about it.
Yes if your mobile platform Symbian s60v3 or s60v5 or you use Blackberry you can easily use your mobile camera phone as wireless webcam by Mobiola. Here is a detailed explanation of how to setup it...
I can't speak for all people, but I can tell you why I have used a web-cam in the past.
The first use of a web-cam was at our receptionists desk. If a visitor came in for someone, you could hit...