When someone buys a share in Apple, they actually get an ownership share in Apple.
Apple, yes. Google or Facebook, no. Google and Facebook have two classes of stock. The class with all the voting rights is in both cases controlled by the founders. The publicly traded shares cannot outvote them, even if someone bought all of them.
Until recently, multiple classes of stock were prohibited for NYSE-listed companies, which tended to discourage doing this. (The classic exception was Ford, which has two classes of stock, the voting shares controlled by the Ford family. This predates that NYSE rule.)
This matters when the insiders make a big mistake and the stock starts going down. There's no way to kick them out.
It also matters when someone has built something of value, and then becomes publicly traded, since it keeps the financial vampires from descending on the company and sucking the blood out of it, leaving a husk which dies in 6 months. That's what's currently going on with the OliveGarden proxy fight, where a funds group has acquired a large position in the company, and now wants to spin off the real estate holdings to a separate company (taking about $1B in the $2.5B value portfolio as a one time dividend, and putting in their own sock puppets on the board to short-term pump the stock by changing employee mix, etc.).
The problem with Google and Facebook maintaining one class of stock is ISOs/RSUs. Stock given as incentives to employees, after the vesting period, can be sold on the open market, and if that stock position becomes larger than the founders, then the people who made the decisions that created the large value in the first place are no longer in control, and Gordon Gecko (or Carl Icahn) can come in and do what's best short term for the shareholders, rather than what's best long term for the shareholders, company, employees, and customers.
Who do I trust more to make the best decisions not totally motivated by short term profit, Carl Icahn, or Larry, Sergey, and Eric?
Yeah, there's long term downside risk to the stock as a straight financial instrument (along with significant historical upside), but you know what? I don't really feel the need to destroy things just because that's they path to my highest ROI over time.
For better or worse, I'd rather have the founders, not Wall Street, making the decisions that guide the future of the thing they built.