It's more of a fault of Microsoft. Windows has a huge amount of security holes and Norton expands to try and keep an eye on all of these holes. It's just become bloatware. They also release one version of their software, so even if you're running it on Windows XP, you've got all of the security features for Windows Vista, which was probably the biggest security flop in computing history.

Their overall algorithm hasn't changed in years either. An algorithm that could handle 100 thousand viruses on a 1GB hard drive grinds to a crawl checking for 100 million viruses on a 1TB hard drive.