I can't address everything because my post would get to "ZOMG spork your eyeballs out long" but I think the primary reason that we have yet to have a "name" come out of self-publishing itself instead of after a mainstream publisher backed them is because the stigma of self-publishing has made it such that most SP authors seem to want to "get out of" SP. It's a means to an end for them.
I think this is all a mental block more than anything. There is nothing about publishing as a business model that makes it such that you can't create something that catches on and set up the business infrastructure to handle that success.
While that's not necessarily a bad thing for authors to take a deal, I think it helps to reinforce the stereotype that SP isn't a sustainable business model on it's own. And I believe that it is. When you do the math for 10 years out with 10 books in your backlist, there is a legitimate possibility of someone 'breaking out' in some way AS an SP author without even needing an outside publisher in the equation at all.
I think it takes someone (or several someones) truly committed to the business of SP itself, who can build each success on top of the previous smaller successes. But I think once someone does it, we'll start to see a lot of other someones do it. Because the game totally changes once a possibility opens up after someone has proven something can be done. (Like the guy that broke the 4 minute mile, after he did it a whole bunch of other people did it the next year.)
After a point, if the readership is out there, it's not that you CAN'T get it without a major publisher, you just have to find a way to reach your peeps. And you have to have some business sense and know how to reinvest to get your name out there further.
And I think the best days of SP are ahead of us. I also believe that as we go more and more to Ebooks and Ereaders that there is going to be less of an idea that you can "only" do the big stuff "with" a big publisher.
Because most publishers are not interfacing all that splendidly with the e-world. They don't have giant online presence. The Internet is the Internet and if we're on the Internet an SPer who knows how to market and get their name out there doesn't need a publisher in the online world. They just need to know how to build their platform.
The publisher therefore becomes a middle man.
Zoe Winters writes at zoewinters.org