Open Source radically alters the equation; when I build a system on Open Source, even though I may not have built it, I do own it. I own it collectively, but still fully individually, in a way that really only works for software. As a home user I don't find myself fiddling with source often, but as a professional programmer building on an open source stack I do it all the time, and it is qualitatively different than working on a closed stack.

At PARC, I'm sure the cost of "fixing other people's stuff" was more than "building your own"; a few hundred million lines of code later, that balance has changed a bit.