How safe is the internet?

I wonder about this as I transfer more and more of my important information – files, music, contacts, calendar, photos, correspondence, and more – onto the internet only. (I’m not interested in a lecture that I shouldn’t do that, please.)

I have this fear of one day just getting an error message when I try to load Google or anything else. Is this a rational fear? Or irrational?

What would it take for the internet to be “taken down”? If someone had that intent, how would they do it? Is it possible? Feasible? Is it easily do-able, or is it extremely difficult and un-doable?

(This is a question I previously only debated in the private arena of my mind. But it occurred to me today that I could ask Fluther and actually start to get an answer. How cool!)