Well, a nice economic fightback tactic would be for the ISPs to say that after 1 "strike" (being caused by the user downloading music) the ISP then demands that since it's music causing the problem, the music companies must now strike that person off their own customer lists.
Therefore the person is no longer allowed into any music stores or to buy music from those companies by any means.
Once the labels can show that they are doing their part of the work, they may go ahead and serve more notices for downloading. Once they have shown all their paperwork proving that their culprit has been turned away from stores and the comprehensive list of "downloaders" is being enforced at every outlet, they may go on to strike two and, eventually, 3.
It is unfair that the ISPs are made to do all the work for the labels in this respect AND to cut off their own paying customers who may have paid for 50GB of bandwidth and used a measly 5MB of that (.1%) in order to infringe on the labels' copyrights.