Privacy & lazy admins
As a private individual, why the hell should I be forced to give out my personal contact details to every muppet on the internet who wants them? Apart from preventing a mass of spam, both electronic and postal, being able to hide my contact details in the WHOIS results of my .co.uk domains helps to prevent fraud. Surely no one here would be stupid enough to go posting their home address and phone number on a website forum somewhere, so why should WHOIS be any different.
For companies it's completely different. The registrant details point generally to a companies head office, probably listing the MD or IT Managers name, but there's no information there that you couldn't find just as easily by checking Companies House. You're not getting the home address and phone number of the MD. Besides, in the UK at least all companies are required to have their company contact details listed on their site(s), so listing them in WHOIS as well makes no difference.
In terms of tracking down dodgy sites, how does WHOIS actually help? Since the information submitted when the domain is registered is never authenticated by the registrar or registry, there's no way to be sure that it is genuine. There's nothing to stop me from registering a domain name with bogus details, hell, if I registered micro5oft.com, and set the registered address as a certain location in Redmond, would that somehow make it legitimately connected with MS?
It sounds to me as if all those people talking against this are just being lazy, and can't be bothered to use the correct tools for the job. If there's an issue with content coming from an IP which a domain points to, it's the ISP responsible for the IP that should be contacted, not the domain owner. In many cases where you're dealing with small companies, contacting the registrant direct would be pointless, especially for something like suspicious network activity, as they wouldn't know what you are talking about. All that would happen is that they would then need to pass on the message to their ISP to deal with, thus taking more time to resolve the issue than if you'd just gone straight to the ISP in the first place.
ICANN should adopt the same method as Nominet, plain and simple. (and while they're at it they should switch to Nominet's method of IPSTAG's which makes far more sense that the alternatives, which require all kinds of domain locks to keep secure!)