Google would appear to favour sites that are built by those who know all the SEO best practice techniques and tips. There must be many technically poor sites that actually have fantastic content, surely these shouldn’t be penalized?
They’re definitely not penalized in the sense that they don’t receive any manual action that would make them rank lower. But we do try to compensate if there’s good quality content and people still make mistakes. All the time people ask: “why don’t I get a bonus for having W3C code that validates really well?”
We try to make it so that you don’t have to do SEO, and we still find the good content. Of course, if you’re willing to put a little bit of time into just making sure that your content is accessible, and useful, all those things, that absolutely can help. But it’s definitely not the case that we want to penalize anybody if they don’t do every single thing right on the SEO checklist.
First and foremost, we care about trying to get the stuff that people really will like, the good, the compelling content in front of them. And so we try to make Googlebot smarter every year. And we try to think about new ways to index and return pages. And that’s just something that we’ll keep working on and hopefully do it relatively well.
by Matt Cutts - Google's Head of Search Quality Team