An internet is simply a connection between two networks. When talking about the loosely-connected network of networks that spans the globe, I always capitalize it. For most purposes, I suppose, the reader will generally know which 'net is being discussed. But the tech gurus (who really run the world) need to have ways to differentiate.

Thanks, Brandon, for scratching the itch of curiousity I had as to why Internet is capitalized. [putting on-Carnac-hat emoticon] I predict that, the need of the tech world notwithstanding, "internet" will be adopted by the majority as the proper spelling of the internet, leaving the tech world to designate another method of differentiation.