"6 strikes" rule considered by Internet service providers

Click on this link to read a Washington Post piece (7-8-11) about a rule being contemplated by major Internet service providers (ISPs) to respond to charges of copyright infringement by their users. Copyright holders report (alleged) infringements to the ISPs, but the question is then, what responsibility do the ISPs have to respond--particularly when the same user has (allegedly) violated the copyright more than once. For example, individuals who repeatedly post copyright-infringing copies of songs or movies on YouTube. Taking more strict steps beyond warning the individual user, such as shutting down their internet access, has become more difficult now that many people depend upon internet access for their phone and other services. Taking these services away because a third party (the copyright holder) claims that their intellectual property has been misused puts the ISP in an awkward position, especially if there is controversy over whether the copyright has indeed been violated. The "six strikes" rule attempts to establish a zone of flexibility for dealing with the such cases. It's unclear how the number "6" was arrived at...