A better comparison is Linux on the desktop: I've been assured it's been about to happen for the last two decades by programmers who thought the hard part was writing a kernel when in reality it was all of “boring” work offering a decent user experience.

Similarly, anyone who starts a social project and talks about tech is almost certain to fail, no matter whether they're a bunch of OSS developers or Google, unless they have put even more time into the actual key problem: good user experience.

If you don't have a solid story for how people will find other people they want to interact with, what reasons they have to interact in the first place, and how you'll deal with abuse, nothing else will matter.