User interface fatigue - where are the best practices?

There is big risk in the redesign of a popular web site because people are creatures of habit and nobody wants to have to learn a new user interface. Yahoo has come across this as it changes some of the features of Yahoo Finance, one of the largest and oldest web services on the Internet and users voice their displeasure.

There are already too many user interfaces to learn, too many new "web 2.0" apps to learn, too many new digital gadgets to learn how to use. Every time I change my cell phone I have a different user interface to learn, there seems to be very little continuity.

All remote controls for consumer electronics products seem designed to have unique user interfaces, even within the same company and the same product families. Even when it comes to positioning the power-on switch--there are many forms of expressing what must be the single most common user interface element...

I've noticed my kids always pick up user interfaces a lot more quickly than older generations. They can figure things out more intuitively. Clearly this is a skill that can be learned: quickly learning new user interfaces. But why should we need that skill?

What puzzles me is why isn't there a best practices user interface for nearly every type of electronic gadget? Surely there must be some agreement by designers on the most optimum placement of keys and controls? Our typewriters have a standard interface, and our cars, and our musical instruments, why so little else?

It used to be that companies would sue others for copying the "look and feel" of their product, such as a spreadsheet program, or trash can icon. But such lawsuits are rare these days; yet we have ever more user interfaces to learn rather than some basic standard formats-- onto which companies could add differentiating buttons and controls.

The lack of standard user interfaces must be the single largest obstacle in growing the markets for digital products of every kind. Nobody wants to have to learn yet another user interface when there are so many better things to do.