What is the value of your network?

I think it's pretty well accepted that 'networking' is important for your career, but it's often hard to distill those benefits into one clear assessment of 'the value of your network'. I'd be interested to know how you assess the value of being part of a network (is it about real job opportunities; access to knowledge; access to senior personnel; personal brand etc) and why you invest time/effort in developing your own network. I'd also be interested in any examples of where people have experienced real benefits from being 'connected' as part of a network? A new job? A great idea or hot tip? An invitation to an event? Even a new friend....maybe even a Procurement wedding?! Thanks!