I think style in web design is like style in any art --- you have your abstract style and you have your impressionist style --- and within each style there's good and bad. And each style can be used in different ways to convey different messages, or as you say -- persuade. I think that the right combination of style and color and content does indeed have an effect on the viewer... and I think that a lot of thought has to go into all of those things in order to convey the right message. It all goes back to marketing. You gotta find that golden message, the golden style, that speaks directly to the consumer base that you are targetting. That's why, again, I think that web design is often underappreciated. The good designers know these things and are able to cater to different audiences and use different styles in order to hit those sweet spots.

Just my thoughts.