Haven't RTFA, but it seems that this is more complicated. Accepting your argument that an IP address identifies a Network (really an endpoint as indicated below), and the fact that multiple computers may reside on that network, you have to also accept the fact that more than one operating system may be running on each of the computers located on that network (or even more than one OS per computer). Therefore, since the plaintiffs are looking to recover damages from Microsoft, you can't say that you are entitled to a damages award just because you were assigned an IP address on a given date, and that IP address is reflected in Microsoft's logs for that date. What may really have happened is that multiple Win OS boxes may have been affected, or none at all (if the network was populated by computer running only OS X or Linux). You can't look at the IP address and determine what was happening on the network behind that IP, and that should be the reason why using an IP address as a basis for determining damages is flawed.