Self-Publish Or Go With A Big Publisher
Whereas a few years ago self-publishing may have been viewed as a less credible form of publishing it is now much more accepted as an alternate route, especially with the rise of companies facilitating self-publishing (see Mashables 6 ways to publish your own book)
If you already have a large audience who follow you and like your work then self-publish
Why would you want to give most of your royalties away to a Publisher who will be reaching the same audience that you can reach.
Previously Publishing Houses facilitated the publishing process – instructing typesetters and printers and also carried the costs of book production, printing, warehousing, and shipping.
Today, the publishing process is much easier – whether publishing on the web or in book form and costs are no longer prohibitive. Where good Publishers can come into their own is in distribution with automated systems for alerting their international offices when new books come out which are then listed in local promotional material.
I have seen many instances of successful self-publishing with authors who are experts and have a large audience – but they really are viewed as experts, giving presentations at conferences, being quoted in the press, leading journals, giving radio interviews etc.
On the flip side the media may be more likely to give you attention if you have published with a mainstream Publisher as they will assume that a process of review and quality control has been undertaken – and Publishers are still valued here although how long this will last as a ‘measuring stick’ remains to be seen as products and information are being reviewed more openly on the web.