Elsmarc - 8:33 pm on Sep 29, 2012 (gmt 0)
Yes, but backlinks were always problematic, especially for old, long term sites like mine which are about quite a few topics. There are 10's of thousands of backlinks to my main site from all sorts of sites, but having been online since 1996 that's expected. I had an SEO "professional" look at my site when it crashed and he freaked out at the number, and variety, of backlinks. Supposedly he got into the SEO business in 2002 and a client uses him and recommended him. A few days later he called and said he hadn't worked with a site like mine before and that when he took a close look at backlinks of such long time sites the number wasn't unusual. Duh. No kidding... We talked a bit and he said: "You know more about this than you said you do". I told him I never said I didn't understand SEO having to some degree been doing it for 16 years, but I did appreciate "new eyes" to look at the site.
Their original main signal of quality was backlinks. If someone links to your site, at one time that was normally a signal or vote of approval. But because spammers (or linkbuilders) began creating "unnatural" backlinks to game the system, that signal has lost much of its value.
So now Google may have started using other signals of quality in addition to backlinks. For example, if visitors tend to spend a lot of time exploring your site, bookmarking pages, printing out pages, returning for repeat visits, etc, then these are other possible signals of quality that the algorithm can use.
As to other factors such as time on site, bounce rate, pages per visit, new visitors vs. return visits, etc. - They're not new signals. New signals include visits from social sites such as LinkedIn, Facebook, and Google+. In fact, Google Analytics recently added "Top Social Traffic" to the "overview" in their "Realtime" screen.
That said, to clarify - The site of mine that crashed is a technical discussion forum, not an e-commerce site so when I look at things I also have to ask myself how Google is using an algorithm to "adjust" for those factors. I do consider myself lucky. I have regained 70% of traffic I lost and each week it keeps "getting better", or at least has so far.
As someone mentioned in a recent post in this thread - Going to Google these days to search is very different than it was even 6 months ago. I find myself going to Bing, Duckduckgo, Dogpile (an oldie but goodie) and other search engines. I don't know what they're doing to their algorithm, but it sure makes search a PITA these days. Up until a couple of months ago I exclusively used Google for searches. These days, not so much.