I showed recently Google will use the next available Header, be it a H1, H2, H3, H4, H5 and H6 if your page title element is screwed.

The snippet below shows Google using a H6 header as the page title.

http://www.hobo-web.co.uk/seo.html

Yahoo will actually ignore the Header tags on the same page and elect to use the anchor text of incoming links

Yahoo

MSN / Live seems to just go for it, and index the title as much as possible (@ 75 characters?)

MSN

We've recently updated our comments policy and increased the number of comments a visitor has to make to get seo friendly links in comment signatures to reward long term readers and make it a bit harder for dofollow spammers ;) - I told you dofollow spamming wasn't a long term strategy....