As in subject.
Vsmod can eat over 50% of CPU and can freeze/hardly slowdown PC when playing 720p video on YouTube or other video sites. It really consumes a lot of resources these days.
But it mostly happens with 720p video in browser.
Core 2 Duo E8400
Browser - Firefox 3.6.8
OS - Windows XP SP3
ZoneAlarm Extreme Edition 9.3.014.000