Also, I wanted to ask, what is the difference between advertising on a website by the way of them putting my link on their site, somewhat like the google link ads I suppose, but on a more permanent basis, that is, at what point does direct link advertising for exposure to the traffic of that certain website become link buying?
Should google not try and rely on other variables which are more reliable determinants of quality than links?
Oh wait, I know this one: with the second one Google makes billions.
To your last question, Google absolutely does have hundreds of signals that we use in our ranking; we don't rely only on links. It's a hard problem to assess quality accurately, but we try to find different ways to do it.