Self publishing is no longer frowned upon. Readers do not mind who the publisher is. All they care about is having a good read. The most successful way to promote books is by word of mouth starting with the authors themselves and spreading via their friends and family to a wider public.
Advertising is expensive particularly in this austere age. A large publishing company will always plump for a book written by a celebrity rather than a newcomer because they know it will sell. However, the quality of writing is often poor and the reading public are being let down.
Writers become good writers because they have been plugging away for years honing their art without success because mainstream publishers are unwilling to take a risk on an unknown talent. There are legions of stories of authors who receive rejection after rejection before getting that big break through. There must be many great novels out there which never see the light of day.
Self publishing means that there is now no need for this to happen. It is marvellous that a big publisher has at last realised this. Simon and Schuster are leading the way.