2 points:
1) The only way to ensure that your service won't go down that path is to start your own service you control. Other than that you can't avoid it. At some point in time some giant will offer enough dollars that a start-up won't be able to turn down. The alternative is when the startup goes public and makes its fortune down that route.
2) Investing in these types of companies at an early enough stage where it actually pays off for investors is actually MUCH HARDER than you even described. It's easy to buy a share of public stock. But private share? Before a company is public? You have to be an accredited investor. Meaning, at least $1 million personal network or $5 million in assets, or have made over $200k the last two years and expecting to continue to make over $200k in the next year.
In other words, the regular person CAN'T really invest in a startup. Unless it's your own, your fate is sealed to being the product of startups and will eventually be sold to the highest bidder.