OMG. This is the first time I've heard of the way back machine, and that was WAY too much fun. I found an old copy of Larkenia's Flaws that I'd thought I'd lost when my site had gone down. Totally awesome! *goes back and right click+saves all of the old pages*
Ahem. That said, I'm kinda 'eh' about the web fiction haters. I just don't take them seriously. Haters are gonna hate, and all of that.
People were saying that there was no market for e-fiction for as long as I can remember it existing. Thinking of e-books and blogs, in particular, I remember that for years people said that they were silly and ephemeral, that no real author would write them, etc. And then suddenly the Kindle and other big name e-readers came out and now many of the big name bookstores are trying to cater to them (if they don't have one of their own out, already). Suddenly every local newspaper in my area has a website with e-articles and blogs, to the point where they're cutting down on hard copies of the paper and focusing on the internet version.
As for things disappearing once their gone: I just don't think it's that simple (as the Larkenia instance above shows). I've known authors who've taken their work offline for various reasons, only to have it passed around decades later by people in docs, pdfs, htmls, etc. I've seen fans rally together to post websites and create archives for things that would've otherwise been lost, and I've seen websites that have been abandoned a decade ago standing strong today.
Even if the internet were to shut down tomorrow, I'd still have copies of some of my favorite web fiction saved to things like my e-reader, phone, and computer for reading at a later time. I know that many of my friends do the same thing.
When one of my websites went down a year ago, with my computer dying shortly after, I was at a loss, until a reader sent me docs she'd saved of all of the chapters of my stories, so that I could be back at square one. It was so awesome. *shrugs*
Now, <i>finding</i> things can be a bit tougher when URLS switch, or when content is removed altogether. But, as someone who's looked for rare and out of print books before, I have always felt that it can be just as frustrating searching for print or electronic works.
Mind you, I'm not saying that all electronic works are well archived. Many websites will come and go with nobody noticing. But then again, I think that many print works come and go without significant fanfare, as well.