Hi. Very nice to see you here Matt. Logically, what is the difference between paying for links and spamming sites, or, spamming webmasters, or other active link building practices?
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?
Andrew, the difference with buying normal ads (as opposed to links) is that ads don't affect search engines, while buying links that pass PageRank does affect search engines--and all search engines, for that matter. Imagine if you bought an ad in a magazine and you started to get better "rankings" from the magazine in terms of more positive coverage. Most people wouldn't want that.
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.
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?