If people think this is (just) about stopping crime then they deserve all they will get. This is about the government and other organisations building personal profiles on everyone. The government (or associated profiling organisations) will sell these profiles to marketing and businesses who will use them to 'target' people with annoying e-mails, letters, mailshots, phone calls.
It matters not what promises are made by the government - once the privacy wall is breached it is gone and gone forever, and every person's personal information will sooner or later simply become a commodity to be owned and sold to the highest bidder. The DVLA are already doing this with our personal details. So expect the same with internet usage profiles.