• In the 1950's, the term "mainframe" was used to describe the earliest of computers which were so large they were housed in their own building.
• In the 1960's, the term "mini computer" was used to describe computers that were as large as a refrigerator.
• In the 1970's, the term "micro computer" was used to describe "personal" computers that could fit on or under a desk.
• In the 1980's, the term "luggable" was used to describe a computer that could be "easily" transported around.
• In the 1990's, the term "laptop" was used to describe a computer that was lightweight enough to sit in your lap.
• Today, we have "notebooks" and "netbooks" and "pda's" and phones that are more powerful and have more memory than the original "micro" computers.

With the term "mini" being used to describe a refrigerator-sized computer, it's no wonder the term "nano" is thrown around loosely in many applications.  The fact of the matter is this:  no matter how small something is today, it will be smaller still tomorrow.  Computing power increases while physical size decreases.

We all remember the kids in junior high who had "calculator" watches, and now we have a company putting out a touch-screen phone in the form of a watch. (I've repressed most of my memories of junior high, so I'm not entirely sure if I proudly wore my "nerd cred" back then or not!)

The final thought I have on this is simple:  smaller form factors are MUCH harder to design for than larger ones.  Usability has typically been the sacrificial lamb on the alter of size, but it must rapidly increase in priority for architects and designers.  It's not always easy to sit in front of dual 24" widescreen monitors and design for a screen that will be 3" or less! 

Don't be afraid to start from scratch, because old ideas don't always translate.