This is by design.  Chrome is multi-threaded and will distribute all aspects of the site(especially audio and video) across of all of your cores it can.  This leads to high intensity sites NOT getting slow or having issues provided your bandwidth holds up.  I have seen multiple tweets about this behavior.  It’s been common in many many other apps for a long time…it’s about time web browsers came of age in this regard.  On the Windows front the best browser for MT performance is Google followed by…IE8.  Yes IE8 is partially threaded.  Firefox and Safari are not threaded.  I have had to start using Google more and more because sites are beginning to overload FF and others due to them NOT being threaded.  I won’t USE IE due to it’s near constant Active X issues.  I really hope MS ditches Active X.  IE has really come a long way but Active x still allows IE to be an easy target directly to the lowest levels of your system.

The comparisons of browsers(with the exception of IE) also apply to the Mac as well.