When I studied statistics in college I learned about bell curves. What I didn't realize at the time is how well they reflect the technology industry. Every company and product has a bell curve for a life cycle. They start out small, grow at varioius rates to their peak and then trail off again, back to the beginning.
Historically this is very clear. Look at companies/products like Polaroid cameras, Palm PDAs, Lotus 1-2-3, and just about every other product line and you'll see the curve. Some of the curves are much longer and were much higher, like Kodak film cameras, and some were relatively small and short lived, like Netbook computers. Something totally new came along and replaced them in the market. Digital cameras have replaced film cameras almost entirely and Tablets have replaced Netbooks.
I was impressed with Eric Schmidt's recent letter to Congress when expressed a similar view. In the letter he opined that Google started out small, they have become a power house and will someday be replaced by something like Siri. Very good Mr. Schmidt, when you learn from history you can avoid some of the inevitable failures.