tedster - 6:28 pm on Jan 20, 2012 (gmt 0)
There's no doubt that all search engines have a need to use other signals beyond backlinks. Webmasters here have been crying out for less dependence on backlinks for many years... and it is happening.
This particular signal seems to be a no-brainer to me. That doesn't mean it would be easy to automate in any way. I've been considering how to program a script to analyze a page layout and it seems to be well beyond a one-man job to do it at scale. There's just too much variation around the web.