Knowing what you know now about the growth of the computer industry, the Internet, PC's in every home someday, etc:

If you could go back in time, say ten years, what PC computer company would you invest your money with? Do you think it would be a good idea to invest in the leading maker of PC's; the one with the most market share? Wouldn't they be the ones with the most potential to capitalize on the future growth of the industry? Who is the current leading company in the industry you are following?

In the 80's one of the leading computer companies in the PC industry was Commodore - remember them? At the time, they had all the potential in the world.

Looking forward in the long term it is very difficult (and exciting) to predict who will be the future big players. It will not necessarily be the current big player.  One thing you can do is invest your money into several companies within an industry.  This diversifies you a little and covers your bet.  If one of the companies becomes the industry leader ten years from now, the gains from that one stock should offset the losses and mediocre performance of the others.

Some mutual funds do this for you.