I don't think anyone believes that you enter at the bottom of the ladder of a shop with 10,000+ software engineers and then change anything major. To do big stuff at Google you have to either work there 10+ years or come in from another company having done good stuff.
The only realistic shot for hackers to change the world is through their own startup.
The best part is that the two are not mutually exclusive. Maybe making a startup around mostly open-source code is more difficult, but I think it'd be worth it.
Thousands I guess. Take Wordpress for example. Didn't it change the world? Take PHP itself, or Perl. Didn't they?
Also, I think the phrase "change the world" is overrated. Sometimes it's not less important to keep the world running, which also requires constant work and a lot of human genius.
You seriously don't think Linus is solely responsible for Linux, do you?
He should and does get the credit for having the insight and chops to have started it all, and is the single-most important person for Linux, but today's Linux is the result of the work of thousands of programmers.
rms, jwz, Guido, Matz, DHH, Shuttleworth, even Rasmus, the many contributors to GNU, gcc, Firefox...
Imagine the software landscape as it would be right now with no free software whatsoever. Then imagine the hundreds of brilliant people required to devise and lead each of those projects...
I disagree - I believe that a properly-organized company would give anybody the opportunity to change the world if they were good enough. Two caveats:
1) I do not believe such a company currently exists anywhere in the world.
2) I would have no idea how to go about organizing one.
Listen to this man. I was a full-time software engineer at Google for 5+ years, and I didn't change shit.