All content-heavy interfaces need to strike an appropriate balance between visual simplicity and information density (content, as usual, is defined as the information and activities that constitute an interactive system). Visual simplicity keeps things clear and focused. Information density provides lots of choices to match lots of different user needs and behavioral patterns.
Edward Tufte has been known for evaluating the quality of an interface design by counting the number of links on the screen. That’s information density -exemplified by MSN. The other side of the coin: Google.
“There is a dynamic tension between simplicity and insight which must be dealt with... The danger is over simplification will sacrifice insight into the situation.” -Exploring Visual Information Design (Design Crux)
In an interface design, this dynamic can be addressed with Ben Schniederman’s information-seeking mantra: overview first, zoom and filter, then details on demand. Which, interestingly enough, is closely related to Edward Tufte’s notions of macro and micro information presentations. So the question becomes why does this not seem to be the case in Web interfaces? Why would Tufte consider a home page filled to the gills with links a successful design? Wouldn’t most users agree that home pages are too full of information, too cluttered? Isn’t information overload a serious problem? Couldn’t we gradually reveal information to users?
“People will complain about a visually complex page at the sight of it. But they will also complain if the information they need isn't immediately available to them when they start using the site.” - How visual simplicity can harm usability (GUUI)
A great example of finding the right balance comes not from Web design, but from the BMW iDrive system, the driver/car interface featured in their newest top-of-the-line automobiles. Take a listen (1.9 MB mp3).