Simplicity is obviously a very positive attribute of good web designs. In practice, however, this means different things to different people. There are some cases where the concept of simplicity can be misinterpreted to mean "keep the copy short and catchy." This can actually lead to a less powerful website, effectively making it less usable.
Let's look at two examples of when long and accurate copy is actually better than short and simple.
Company Descriptions
It's always a good idea to include a company description or tagline. It can be surprisingly difficult for users to figure out exactly what your site is about, or what your company does. But many companies who do provide a description make it so short, it fails to give the user any valuable information.
Accenture, for example, says they're about "High Performance. Delivered." This may be short & catchy but contains virtually no content.
Notice that Booz Allen, one of their competitors, does a better job: while their description does contain a branding slogan, it also includes a long descriptive part to help the user get their bearings. This is a case where long and accurate is better than short and catchy. (For an example of an even longer, more accurate company description, try my company's homepage.)
Product information
While it's easy to overestimate your user's tolerance for complexity, I find it's just as easy to underestimate their appetite for detailed product information. Once users identify a product they're interested in, they often develop an enormous appetite for the most detailed specifications. No wonder Amazon's product pages have grown so long over the years! Try to anticipate any question a user might have--this can include questions about size, materials, quality, design, how to use it, how it was created and how to take care of it.