Re: I do wonder...
Black text on white is the most* familiar to those who grew up using pen and paper.
Blue is easy on the eyes* and a relaxing colour* because you don't want people getting angry navigating your site. Blobs of blue are also easy to spot* on a white background, which is important when the button says "Buy now"
2D flat is the visual style du jou^H^H^H decade
That being said, on any site that will give me the option, I'll have a dark grey background with white text as it's far easier on the eyes.