It was certainly true at large LAN parties. I had to reinstall Windows at QuakeCon one year, and it was nearly impossible to win the race against the malware floating around the network. Putting your computer on the same LAN as 3000 gamers (most of whom download a lot of warez) isn't exactly the same as connecting your computer to the internet through a firewall, so I'm not sure if my experience at QuakeCon generalizes to a typical PC setup.