Up until now, surveys carried out of Internet traffic have found that a bulk of the traffic is from file sharing networks such as BitTorrent.  Some ISPs are also infamously known for throttling such traffic or in some extreme cases even blocking it.  Now ISPs in the UK are getting aggravated over a new bandwidth hog - the BBC iPlayer.  This service will allow British users to download BBC content for free within the UK, however, the beta version released just last month has already been reported to upset ISPs over the bandwidth requirements.  For example, Tiscali UK complained that it would congest its network to the point where it would require network upgrades, while other ISPs say they may have to increase the price based on usage or apply traffic shaping for video traffic to give priority to other traffic.

The content offered by BBC's iPlayer is free and funded by TV license fees, but is infected with Windows Media DRM where the content expires after 30 days of downloading and only plays on PCs running the Microsoft Windows OS.  Content is distributed using a peer to peer network approach.  As the BBC aims to make its archive of about 100 years' worth of content available through its iPlayer service, this will potentially attract a lot of consumer interest very quickly. 

The service is not available outside of the UK or to Linux or Macintosh users, although the BBC announced it is working to make the service available to other platforms.  At this time, there are about 7.2 million IPTV subscribers in Western Europe, although it is unclear what portion of these are UK IPTV subscribers.  This figure is expected to increase to 21.3 million by 2010.

Further info can be read in this source E-Commerce Times article.