I am the editor of a peer-reviewed technical journal.
The Society that publishes the journal has strict rules requiring that the editor be unbiased and impartial. While there is no prohibition against the editor submitting work to the journal, there is an absolure requirement that the editor recuse himself from any editorial decisions regarding his own work.
My personal view is that I must take things a step further and make sure that there is never even a question about my integrity. That means that I have imposed on myself the constraint that I will not submit work to the journal during my tenure as editor.
Applying that principle to Ian's more generic question, I believe that it is unethical for an editor to use the publication's mailing list to sell his own work. I know Brooks Jensen sells his work through Lenswork, and Steve Anchell advertises in Focus - to me, that seriously compromises their integrity as an editors. And while I know this observation may irritate some folks, I have to point out that Steve Simmons does NOT sell his work through View Camera.
There is actually a broader question - is it proper for the editor of a magazine to engage in any commercial promotions. My view on that is that promoting the magazine, growing its circulation, and agressiving shilling commercial ventures that are part of the magazine publication business do benefit the editor. But these things are part of his job, and the benefits are not limited only to the editor. So the key consideration is whether the commercial activities that editor is promoting benefit only the editor (in which case there are ethical issues) or whether they benefit the general ownership and staff of the publication (business is business).