Yes ISPs collect logs. They also do not release them to anyone, not even LE without a court order. In fact one site, Torrentspy, was actually ordered by the court to begin keeping such logs and to turn them over to investigators and chose to shut down instead of doing so. Any ISP found to be doing so would be in breech of Canadian Internet privacy laws. In cases of child porn, any ISP will cooperate with LE without any court order or warrant. YVO, I would like you to show me one case of an ISP disclosing their user log information to anyone without a court order.
The problem is that they do! And not just to LE. The amount of data warehousing that is being collected is phenomenal! Its a marketing all you can eat buffet.
The only advantage is that all this information is not correlated into centralized DB's. Google does correlate its information , with Reveneu, etc etc.
Though some LE agencies do get multiple sources from ISP, Financial, Gov agencies, they correlate this info into a patterns and profiles, based on chaos engines, from these patterns they get trends and baselines. But they also can isolate any individual and trace his/her movements based on the source.