I had a similar realization this year. For the first time I realized I knew people who currently work at, or very recently just worked at, all the big software

I had a similar realization this year. For the first time I realized I knew people who currently work at, or very recently just worked at, all the big software companies: Google, Amazon, Apple and Facebook. It may be partly helped by age, but also perhaps if you've ever worked at a large company with a ton of engineers, then leave, and those seeds scatter, eventually at least one ends up taking root at each of the big shops.