What Makes A Good Blog Header Design?

Im wondering what those of you who run blogs thought about the design of the header on a blog, do you think the design/layout of the header itself is as important on blogs as other types of website?

For example, i have seen some blogs that do not have headers on them at all, not even the blog name and others i see have graphical headers ranging from really basic text on a plain background to fancy high-end designers for their headers.

How important do you think the header is on a blog and, what makes a header design 'good' when it comes to actual blogs?

Regards,

Lee