Text messages turned out to be a great tool, created more or less by accident and intended for a completely different purpose.
Twitter is something no-one asked for, but it changed the very landscape of mass communication. Its more like a tool that has shaped the world around it.
Wikipedia is a fantastic tool. It was essentially created on a hunch, that a crowd-sourced encyclopedia would work. Deep analysis of the fundamentals of knowledge and how people work together to shape it was not necessary for it to be built. It was more like 'this is possible, lets try it'.
The internet is basically layers of hacks, each bent to a different purpose from the original design. If you try to design something like the internet and make it philosophically pure, you end up with Project Xanadu. Which doesn't work.
Facebook's model of how human friendships work is laughably simplistic - binary on/off friend/unfriend. There's no insight there. If the Social Network is to be believed, Zuckerberg's main insight was to build something that would help harvard students get laid. But still, Facebook works as a tool. Google Plus tried to have a more accurate model of relationships, and made it too complicated. Perhaps insight is a disadvantage? A good tool should be about the possible.