Actually if you want some feedback on this from a published and author you should read the site/blogs of my favorite author Lawrence Watt-Evans:
http://www.watt-evans.com/
He writes books the "traditional" way and also in reader supported serials, in the case of the serials if he gets sufficient donations for a particular work he essentially becomes his own publisher and has the print book mass produced and distributed.
He was also an early adopter of the ebook format and insists that his works are distributed DRM free, he relies on the fans to support him by purchasing the books, his print editions or by donating to his serials. But feels the DRM systems are awkward and unreasonable.
Despite his strong support of ebooks he still does books the traditional way as well (as a fan I wish all of his books were available in ebook but some of his publishers restrict that) He is clear how using a publisher benefits him:
If you compare his serials to the published work you can see the work done by the copy editors (and if the work is copy edited by the community I don't see any author getting paid, everyone will read it and consider themselves editors)
The publisher works as a form of insurance to him, they have lawyers and financial reserves by which to protect the authors IP rights - J.K. Rowlings will also speak strongly of this function as random house lawyers have worked hard on her behalf protecting her money when pre-releases were leaked to the web or fan translation were released prior to the official translation.
The publisher pays him in advance for works, and guarantee certain payments on delivery of finished work, giving him the ability to dedicate his time to writing knowing his children will be fed. Pier Anthony spoke on this in his author's notes during his Xanth days, he apparently came up with MANY book ideas and would submit them to the publisher, the publisher had a team to provide reader feedback and would base their offers on that feedback, he would then write the books he knew he would be paid for.
Publishers handle publicity, you can speak all you want about ratings and reader recommendations etc but there is a HUGE and I do mean HUGE volume of readers that essentially don't think for themselves, I know readers and not thinking sounds like an oxymoron but it's true. Many people don't buy an author until a certain person (can we say Oprah) or reviewer tells them to. It's the publisher that gets the book into the hands of those important people and its all $$ based. It's also the publisher that gets those exciting little review snippets on the jackets and and again I've seen people making book choices simply because of how those mini reviews sound.
Yes I'm reading/hearing the stuff on the art tax and how much a medium shift requires a shift in business etc etc. It's nice sounding but it's not going to happen, at least not in the next decade. Too much would have to change we just barely got China to agree to the current copy righting/author compensation policies, you think tomorrow they'll agree to pay taxes to an author fund instead? Also thousands of content authors particularly in the music industry are bound by legal contracts that would prevent them from publishing in a web 2.0 medium. If there is a system coming down the line that might eliminate publishers you can be sure that they will be writing very creative and binding agreements that will preserve their rights to control those content authors.
Also speaking of those other mediums without the legal contracting etc who controls the compensation in group endeavors? Take a research work that was written by 5 authors, who decides who gets what for a particular work? Even if they are paid in the tax based on the success of previous work who decides how much credit each author gets for this work. Or for a hit song how much is the singer, how much is the band, how much is the mixer, how much is the lyrics and how much is the music (you know the beat etc - there is a word for it but it escapes me right now)