The logo should be clean and authoritative.
I would prefer a graphic of a sexy model that has a modern, flat, vector feel to it. I'm open to other ideas for graphics as well and even something abstract if you think it will work better.
It should be useable as a watermark as well. So that means text should be readable when resized down small.
It's a plus if the graphic part works both above the text and to the left of it. That way I can use it when different aspect ratios are needed.
Another plus would be being able to use it on different colored backgrounds and even over photos of different colors and textures. This is a lower priority as it can create some pretty serious design limitations and I'd rather optimize for the more common scenario.
Also, keep in mind, any colors used in the logo will probably be incorporated into the color scheme of the website. So this probably means a highlight/background color and a text/foreground color. There should be enough contrast between them to make the text legible and clear when combined as a foreground against the background color.