The other day, Steve Plunkett asked Matt Cutts of Google, what percentage of penalties/filters are based on violations of Google's Quality Guidelines versus technology issues or bugs on the webmaster side?
matt Cutts responded that "almost all for quality violations." Matt added that "violations of tech guidelines typically just result in those pages being pruned" instead.
I don't think this comes to any as a surprise but good to have in writing.
Forum discussion at Twitter.