I've actually never seen a black/white/grey web 2.0 site, so maybe I just live in a box or design in an odd manner. Most of theones I've seen or worked on used rather bright saturated fun colors, kind of reminiscent of Apple's fruit colors. When I learned how to design web 2.0 designs my criteria were:
* Simple layout
* Centered orientation
* Design the content, not the page
* 3D effects, used sparingly
* Soft, neutral background colours
* Strong colour, used sparingly
* Cute icons, used sparingly
* Plenty of whitespace
* Nice big text
but shades of grey isn't on it.