ID a DSL user through subnet data?

I realize that this is not linux specific, but here goes:
There has been a lot of recent discussion on the acquisition of P2P
companies' logs by the RIAA/MPAA. Some posters on various forums claim
that if the RIAA/MPAA obtain the logs for p2p companies, they can then
in turn sue those who have downloaded files from those p2p networks. Of
course, it seems to me that the RIAA/MPAA would have to get
identification data from the ISP. And SBC has been asked by the RIAA to
hand over that data, but they refused, and have gone to court.

However, if SBC does lose, and hands over the data, I wonder how long
they keep data that could identify a user of a p2p network. So I asked
SBC what logs they keep and how long for DSL subscribers. THey told me
that they keep only subnet data, and not what IP number a particular
subscriber has at any particular time. That subnet, they say, would
include probably hundreds of subscribers. THey neglected to tell me how
long they keep that data.

So, my question is, how could the MPAA/RIAA use subnet data to ID a
user of a file trader, if they had obtained an IP number from the logs
of a p2p network, and SBC gave them only subnet data, which apparently
would consist of a list of maybe 100 subscribers who might have had
that IP at that time.

"randy" <(E-Mail Removed)> writes:

>So, my question is, how could the MPAA/RIAA use subnet data to ID a
>user of a file trader, if they had obtained an IP number from the logs
>of a p2p network, and SBC gave them only subnet data, which apparently
>would consist of a list of maybe 100 subscribers who might have had
>that IP at that time.

With any sort of PPP system, including PPPoE, there should be logs
of which IP was assigned to which authenticated user at which time.

From these logs, given an IP address and a timestamp, it should be
possible to identify the user who authenticated that session. Once
this data is involved in legal issues, SBC will have to retain it
until all related cases are settled. Otherwise SBC could be charged
with obstruction of justice.