Simsi - 6:29 pm on Jan 23, 2011 (gmt 0)
Surely bounce rates hold the key to determining low quality sites. How they are measured and evaluated is down to Google but at the end of the day vistors aren't going to hang around a crap site. That's the way I'd do it anyway.
That would be best for everyone IMO - searchers, Google itself and webmasters. Quality site owners wouldn't have to worry about getting caught in the net then.