OK, to clarify I still think you should rely on the application to handle invalid domain names so you don't break email ect. The problem is when someone creates a Malware site called microsof.com and it immediately compromises the browser of anyone who mistypes the domain name. Granted, the browser could keep a copy of bad domain names and worn the user, but Norton DNS could also do that same job. After all if you are going to query a system to find the IP address it might as well tell you as much as it can when it's responding. It's a packet based network and there is close to zero overhead to doing so.

Now I would hate it if my ISP where to institute such a practice but an independent DNS that let's me avoid most malware, spoofing, and parked domain names. Count me in as long as I can opt out at any time.