If there were no advertising on the web, I can't help but feel it would still be nothing more than a large internet newsgroup/forum without much that makes it the rich experience it is today.
I guess my point is things like Gmail, flickr, last.fm etc would struggle to exist on subscription only. Perhaps we can do without them all though?
Also, I agree with the poster below with regard to finding content these days, it can be tedious. A search on a subject can find pages of aggregators, e-commerce sites and little in the way of true content. I don't find this the norm, but it happens.
That is my point. I liked it a lot more before the commercial web took over. Once, the web was 99% content. Now it's a real effort to find anything worth reading.
If you call your average vanity page "content", then sure, that's true...