A recent survey by Sandvine provided some colour in terms of bandwidth consumption:
1. P2P file sharing applications: 44%
2. Web browsing: 27%
3. Media streaming: 15%
4. VPN: 6%
5. Newsgroups: 6%
6. Online games: 1%
7. VoIP: <1%

Media/video applications acount for almost 60% of the traffic (traffic, not users or time spent). It puts things into perspective and explains why the debate around net neutrality is so important. Just imagine the amount of required investments Verizon, Comcast or BT would have to finance to ensure their networks can support a 100% penetration of video/applications. The issue being that in today's world they can't charge more depending on the traffic type, a byte is a byte...

Also interesting was the relatively high level of VPN usage (more travel? more flexibility?) and the low number for online games. Online games are extremely bandwidth-efficient (most of the processing is done locally and only a limited amount of data is shared with the servers) at the opposite end of P2P applications.