Another interesting question came up in a Google+ hangout from last week. Google's John Mueller said the title tag on the page is not as critical for ranking than the content on the page. In short, he explained that Google can rank a page with a missing title tag, but missing content makes it much harder for Google to rank.
As most SEOs know, content is critical for Google to know what the page is about. But the title tag can often seal the deal for which keywords the page should rank for. All John is saying is that not having a title tag won't prevent the page from ranking, but not having content on the page can.
John said this at the 57:30 mark into the video. Here is the transcript:
DANIEL PICKEN: I had a quick question. And John, it was about something you said a few weeks ago, actually. You said the title tag is a ranking signal, but you said that you use a part of the title tag. And that's really stuck with me. And I was just wondering what you meant by that, when you say you use a part of the title tag as a ranking signal.
JOHN MUELLER: We use that just as a part. I think it's not like the primary ranking factor of a page, to put it that way.
DANIEL PICKEN: Right.
JOHN MUELLER: We do use it for ranking, but it's not the most critical part of a page. So it's not worthwhile filling it with keywords to kind of hope that it works that way. In general, we try to recognize when a title tag is stuffed with keywords because that's also a bad user experience for users in the search results. If they're looking to understand what these pages are about and they just see a jumble of keywords, then that doesn't really help.
DANIEL PICKEN: And you said it wasn't critical. What would you deem as critical to a page?
JOHN MUELLER: More like the actual content on the page.
Here is the video embed at the start time:
Forum discussion at Google+.