Suppose you've made such a prediction about a tech company. How do you act on it? You can buy stock, of course, but is there a more powerful action available?
Note that unlike suggestions to purchase stock in the company, this advice applies to technology at private companies, as well.
In all these cases, the choice is always "Work for us or pay us back" - I don't think you can structure a contract so that they must work for you without running afoul of the 13th amendment.
Shorting the competitors because you think a company is going to do very well is actually a bad idea -- it's entirely possible that Microsoft would have been able to open another very profitable market.