It's a very grey area. Whilst peoples privacy should not be infringed in any way, if they are under investigation, with a warrent, there should be instances where details should be requested & submitted. Child Pornography, Hacking etc etc. Conducting illegal activities online should not omit you from the normal course of investigation. Offline, peoples phone records & house can be searched, online the same should apply. This, ofc, raises the Big Brother question, but I feel as long as it isn't abused (and I'm aware it may be), investigations should not be infringed by Privacy Rites as long as the investigations themselves are done legally.
You need a search warrant for that and I see no reason why such a law should not extend to online as well.