In Answer to Patry's Comments Below...
My response was lengthy enough that I thought I'd make this a separate post.
Patry, I'd say always read submission guidelines carefully, and always be up-front about a poem's publication history so that an editor knows exactly what he or she is considering. At TNHR we have a fairly strict policy of only accepting previously unpublished work.
As to the experience you mentioned above, I think there's a relevant difference between the availability of print vs. online journals. If a poem was published in a print journal with a very small circulation, some editors may decide they want to present it to a larger audience by re-publishing it. If a poem has been published online, however, it is already accessible to a very large audience--i.e. anyone with internet access. Ultimately, this is the editor's decision, and if you are uncertain about a particular journal's policy, it's probably best to query.
Blogs are a kind of gray area, I think, because the audience for individual blogs varies greatly. But if all the poets in this month's issue of Poetry had blogs at which they posted their own work, what would be the point of buying or subscribing to Poetry? The magazine would simply become an index of the best (or the editor's favorite) poems available elsewhere.
As an editor, I imagine readers will like our poets' work so much that they will want to seek out more of it, and I'd prefer that a Google search not bring up multiple examples of the poem(s) we published.
Finally, whether they articulate it or not, I think most readers still believe that the work editors do is important--both in separating the hits from the misses (because even great poets have both), and in ensuring a regular and healthy influx of new writers into the public consciousness. After all, an abundance of poetic talent does not necessarily go hand-in-hand with a knack for self-promotion, and most readers are not going to wade through vanity publications looking for interesting new writers.

Comments
Ginger, Thanks so much for the thoughtful response--which undoubtedly many people have benefitted from.
I agree that the reading public needs editors to separate the serious from the un- or however you want to classify it.
On the other hand, I have to say that after publishing in about 50 literary journals, I was never approached with an offer to do a collection. A couple of months of cutting and pasting old poems onto a blog did that for me--though of course, many of the poems had the imprimatur of various litmags.
It's an interesting topic at any rate: how the internet will effect lit mags and vice versa.
Thanks again.
Posted by: patry Francis | June 22, 2005 05:22 PM
So, say someone had thrown some poetry up on a blog that pretty much only his/her spouse reads, and then one day said poet thought, "I wonder what it would be like to try submitting a few of these to the New Hampshire Review?" Would simply deleting the submissions from the blog suffice?
(Obviously, said poet is a total novice to this world of serious/published poetry -- and is skeptical that his/her work rises to the anticipated level of TNHR -- but should talent one day emerge... )
Posted by: KW | July 15, 2005 10:09 AM
Sure.
Posted by: Ginger | July 15, 2005 12:42 PM