Overcomplicated and "busy" design hinders people from understanding the message they are meant to receive. This means that the information intended to reach the target audience is often lost in the clutter of messy web pages full of irrelevent banners, ads, navigation bars and excessive graphical elements.

Simplicity is often overlooked as websites seek to bombard their visitors with as many options as possible in the hope that they will find something to their liking.

In reality - its more likely that the information overload will result in user apathy, and too many options will often lead to frustration and a decision to leave without making any choices at all.

After all, we all have better things to do with our time than try to work out exactly what we are being served.

 "It’s crucial to have simple web designs to allow the user to quickly find the information they need, especially if you are selling a product. If the page is cluttered with useless text, widgets or unrelated products, the site becomes meaningless.

However, it’s become a common practice to do just the opposite. e-commerce sites have taken this “scatter shot” approach of trying to slap the potential buyer with as many options as possible. Instead of making the landing page solely about one product, sites usually clutter the page with unnecessary information, ads and related products. "

Glen Stansberry, taken from http://www.smashingmagazine.com/2008/08/26/how-simple-web-design-helps-your-business/