This has generated a bit of a debate amongst some of my students, and in the May 2012 issue of Writers' Forum (yes, it's not even the end of March yet, but the May issue is out!) Elaine Everest wrote to the letters page stating that, in her opinion, the practise is unprofessional and an awful idea. (But at least she's got a new Moleskine notebook out of it, having taken the trouble to write a letter to the publication!)
I can understand the thinking behind simultaneous submissions - it can take ages for an editor to respond, if at all. There is an argument that if an editor likes an idea, they will get back to you quickly, and if not then they won't bother at all ... although my latest commission, received on Friday, came from a pitch I made in the first week of January.
I often pitch many editors with the same basic idea, although the treatment of the idea will vary for the editor's readership, therefore I'm technically offering different ideas/articles to the editors - because each pitch will have a different angle.
There is also one other important point to note - market reach/size. The author of the original article in Writers' Forum was an American-based writer, so was writing about his experience in the American market. Because of the vast size of that country, it is much easier to sell the same article to many different publications because their readership does not overlap. An article about seven ways to save money could be sold to a New York circulation magazine, a Dallas circulation publication and a San Francisco publication, without the readership of either of these publications overlapping. (The writer could even specify selling to each publication First New York Serial Rights, First Dallas Serial Rights and First San Francisco Serial Rights, purely because of the size of the country.)
At the moment, I feel that submitting EXACTLY the same idea to two, or more, publications at the same time is asking for trouble. Whether I still think that in 2015 will be another matter. Perhaps I'll come back to this topic then!