Here is the problem: You do not know what Google deems a "quality" site nowadays.
Chances are you can have a clickbank/aff-link on your site and Google MIGHT slap your site simply because you dare to sell something as an affiliate. We had this happen in the past where Google literally terminated the majority of PPC ads and advertisers, simply because they were affiliates.
So..what is a "Quality Site"? You do not need to tell me or any other halfway smart webmaster that a quality site means good, helpful, unique etc. content, good navigation etc.. BECAUSE WE ALL KNOW THIS.
But i think there is more to it. I personally have/had one site which was at TOP Google position for almost 5 years in a row now, with unique, helpful content etc..this site is now literally gone from #1, #2 on Google...vanished. The only reason i can think of is the fact that Google knows it's a site where i link out to clickbank. And i *suspect* (i do not know, i suspect!) that this is one thing they are doing, in the same way they canned all PPC advertisers promoting something from clickbank.
Short: As soon as you *dare* to sell something on your site and make your site with (God beware!) the intention to also make money with it..you have to be careful. Just my $0.02