For example, many Flash websites rely on “rollovers”, which pop up menus or other elements when the mouse arrow hovers over a specific spot. Apple’s revolutionary multi-touch interface doesn’t use a mouse, and there is no concept of a rollover.
This is something I have been thinking about myself, the idea of “rollover” is completely gone in a touch interface. Much like the real world, we scan, we zoom in, and we select. Could you imagine a world where every object your hand moved over glowed or pulsed? Not only would this be exhausting visually, it would be completely worthless, because the brain has already processed and analyzed the available choices, so there is no real need for an extra layer of assurance.
In OSX, rollovers are kept to an extreme minimum, primarily in hierarchal menus where one’s position needs to be tracked. In Windows 7, the rollovers are borderline ridiculous, every single damn element on the screen glows when your mouse moves over it, and the result is tiring. An immediate reaction to a stimuli forces the brain to respond. When an element says “Hey! You just rolled over me!” the brain has to, at least for a split second, acknowledge that an event just happened. Ideally, instead of processing frivolous bits of information, the brain should be scanning over what is already in front of it, gathering information as to how it wants to proceed, and then deciding. This is the beauty and power of a touch interface, it allows for quiet absorption of information.
In terms of web design and usability, this basically just means that we need to focus on the basics: a sensible hierarchy and making sure a user knows something is clickable. Too long have web designers relied on the “hover” event to showcase interactivity. Forcing a user to interact to discover interactivity is crazy.