I can, (and usually do) quite easily get by without Microsoft, Intel, Amazon, and Apple. I'd love it if everyone dumped FaceBook. Google would be more difficult, but not impossible. Part of what keeps these companies going is the inertia and "friends" factors, but much of it is that people like how well they work. They have to keep in mind that they're one good competitor away from having a serious chunk of their business taken .... assuming they don't just buy out the competitor.