That's not really the right question. If Amazon's strategy is hugely successful, but everyone else already thought Amazon's strategy was going to be even more hugely successful and had priced that in, then you could be 100% correct about your question and lose money.
Yet, Amazon is about 100% more valuable stock wise in 2016 vs. 2014. The strategy is about the same.
The real question is: "How will stock X perform vs some baseline". I use a 90/10 VTI/BND portfolio as that baseline. If you have the time to understand how to answer that question, you can make a good return as an individual investor. (Either by identifying good investments, or reverting to the baseline)
For example, if as a tech person, you used your insights into the industry and ended up picked any one of Amazon, Apple, Red Hat, Oracle and/or Google as investments 10 years ago, as part of a diversified basket of 4-5 stocks, you would have beat a safe Boglehead portfolio by a significant margin, even factoring in the market implosion in 2008/9. If you picked Apple or Amazon, you hit a home run.
It depends on your needs though. If you're saving for college and your kid is 16, you need a portfolio with a lower volatility. If you're retired and need income, you want to minimize volatility and minimize tax impact. If you're a mid-career professional like me who won't need a dime until 2030, you can take more risks.
Well, sure you did. If you picked Yahoo in the late 90s, a home run hit you. If you picked Intel or Microsoft in the recent past, nothing happened to you.
A good article on using insights as a tech person is Phil G's piece on shorting Microsoft in the 80s. (Microsoft was much less appealing to a tech person in the 80s than it is now, and a much better investment.) http://philip.greenspun.com/materialism/money
This is not to say that tech people can't make money banking on their instincts, just that I personally am not tremendously confident about my own instincts. I can certainly make a very compellingly sounding bull or bear case regarding any currently famous tech company.
A great example from recent history is LinkedIn's stock tanking hugely in one day and then Microsoft bringing it back to the original level in one day some time later. And I'll be damned if Microsoft ever makes that money back. But I totally should have bought the dip.
To abuse the baseball analogy, even exceptional hitters don't get on base > 60% of the time. If you picked Red Hat or Oracle, you didn't hit a home run, but you still beat the VTI.
That's why you diversify. One safe way to do it is to buy the market. Another way is to buy a basket of diverse stocks. That basket is a higher risk but also has a higher potential of reward.
It seems like we're agreed that investing should not be done by reasoning like "Amazon's strategy for the next couple of years involves X, Y, and Z, so I think they will be successful/fail."
> For example, if as a tech person, you used your insights into the industry [...]
... then I would be radically under-diversified. If tech is doing well, my biggest asset (my career) is performing well. I'm most likely to need to draw on my stocks in an emergency precisely when they'll be doing poorest.
Value trades rely a bit less on others' expectations. If you were to buy a company trading at 12x earnings with the expectation that earnings would grow 15% per year over the next five years, then it's pretty likely that if your expectations come to fruition then you'll make money on the trade.