The less obvious danger of p2p
Many users will associate the words 'p2p' with downloading movies and music online when they know they really shouldn't be, but this is in fact just a protocol implying connections from an end user (peer) to another user as opposed to the traditional link between a server and a user. This technology is a distributed delivery mechanism which is more difficult to control and thus has been very effectively used for illegal file sharing.
Recently a number of companies have talked about using this technology to lower their own distribution costs including the BBC and Sky. This 'legal' version of p2p does however cause some great concerns to ISPs as they see this as an attempt to offload the traffic costs onto their network. Since users are still mostly on unmetered packages they would be unlikely to worry about their computer being used to distribute the movies they view to others who request them (although some privacy advocates might question this practice in itself), ISPs are going to see an increase in traffic resulting in higher costs, if they want to maintain the same level of service at peak times. This may be a catalyst to move fully to charging users for their actual Internet usage.