According to John Mueller, Google’s Webmaster Trends Analyst, in his scheduled Hangout on Air on Google+ posted on YouTube, backlinks are indeed important but not the sole factor in Google’s ranking. It is actually possible to have a high rank even without backlinks.
During the hangouts, Josh Bachynski, an SEO Consultant and Researcher had asked why backlinks make so much importance in ranking and in his personal opinion maybe it could be a good time that Google could start ranking using other factors other than links.
Mueller sited an example that a friend in Zurich founded a website for the local neighborhood without any links. It has about 300 indexed pages which are actually ranking and getting a lot of traffic. He shared that it has no links and it was not linked but it only submitted sitemaps to Google and have an RSS feed. The site is doing well even without links.
Furthermore, he said that backlinks is not the only factor Google relies on. Links are important as it is a great way to build one page to lots of other pages but it is a challenge for search engines to find other ways to rank sites. He shared that search engines had always been using links to rank sites for a long time and many are used to it but that does not mean that it is the only way it could be done.
Mueller also shared that things always change. He said that other factors to rank might be the contents of the web and recommendations through friends. He further explained that the traffic of the site does not also depend on the links but also on the site itself.
If the context of the site gave a great user experience then naturally it will generate traffic as many will recommend it to their friends, for example on Facebook and it might be even viral.