The FBI wants ISPs to retain subscriber info for up to two years including such information as IP addresses assigned to someone when they log in.
Retaining the information is is a burden to the ISPs. It's not actually the retention that's an issue. It's collecting the information in the first place. Networking gear will assign IP addresses without necessarily hitting some central server to log who it is. ISPs would need to make possibly expensive upgrades to actually collect this type of data.
But when the data is not horrendous to collect, I think they should collect it. And they should provide the data to the FBI when the FBI is able to prove to a judge that an internet crime has been committed. After all, this is the sort of data that can be used to catch scammers who use the internet to perpetrate their scams.
However, the rules should be clearly defined by Congress. No fishing expeditions. And the FBI shouldn't be able to use the information to find out that I like to surf web sites that some may consider unsavory. (Or to find out who is surfing those web sites.)
