Criteria for accepting an invitation to become an editor of a scientific journal Yesterday I receivied the following letter:

Dear Tomaz Pisanski,
I am writing to introduce the XXXX to you. XXXX is a new journal launched by the YYYY from USA. With an open access publication model of this journal, all interested readers around the world can freely access articles online at http:ZZZ without subscription.
  We are soliciting scholars to form the editorial board. If you are interested, please send your resume along with your areas of interest to WWWW. Manuscripts should be submitted to the journal online at: http:UUU. Once accepted for publication, your manuscripts will undergo language copyediting, typesetting, and reference validation in order to provide the highest publication quality possible.
Please do not hesitate to contact me if you have any questions about the journal.
Editorial Office
YYYY

I removed the actual journal title and other details since they are not important for this
question. I would like to have some general criteria or guidelines that would help me decide 
whether to accept such an offer or not. 
 A: I am some combination of being too junior and not eminent enough in my field so as to have never received a request to be an editor for a mathematical journal.  But here are the criteria that I would use if I were ever in such a situation:
1) If the journal already exists, then it would have to be one that I respect and probably one that I have already published in.
2) If it is a proposal for a new journal, then I absolutely would have to know (at least by reputation) the person who is contacting me about the journal.  Moreover it's better if it's someone that I and the rest of the mathematical community esteem very highly (e.g. better an offer from Bjorn Poonen or Kevin Buzzard than one of my close friends from grad school who is now an assistant/associate professor somewhere).  I would also like to know who else they are considering for the editorial board.  I wouldn't even reply if the letter were from a publishing company or someone whose identity I couldn't figure out.    
A: It also sounds strange to me. I would think that an offer for an editorial post would be via your peers, or those whom you might consider your academic elders. You should be familiar with the journal, its content, its editorial board, and probably have published an article therein. 
The journal office may wish to have your CV on file if you were on the board, but it is doubtful that they would ask for it if they already know who you are.  
A: What strikes me most is that this letter is generic and not directed at you specifically, in the sense that there is no explained reason why they contacted you and not someone else.  And "highest publication quality possible"? Please.
A: Sorry for answering my own question, but the e-mail I received today may explain that
one really has to think twice before making the decision.

Dear Tomaz Pisanski,
I am writing to introduce the Applied Mathematics (AM) to you. AM is a new journal launched by the Scientific Research Publishing from USA. With an open access publication model of this journal, all interested readers around the world can freely access articles online at http://www.scirp.org/journal/am without subscription.
We are soliciting scholars to form the editorial board. If you are interested, please send your resume along with your areas of interest to am@scirp.org. Manuscripts should be submitted to the journal online at: http://www.papersubmission.scirp.org/login.jsp. Once accepted for publication, your manuscripts will undergo language copyediting, typesetting, and reference validation in order to provide the highest publication quality possible.
  Please do not hesitate to contact me if you have any questions about the journal.
Editorial Office
  Applied Mathematics
  Scientific Research Publishing, USA
  Email: am@scirp.org
This message was sent to [tomaz.pisanski@fmf.uni-lj.si].
  Unsubscribe at any time by clicking here.

A: I wouldn't touch this with a barge pole. It reads like a Nigerian scam.
A: I can't say anything about this particular email you received, but I have received invitations to join the editorial board of two journals, which I declined.  One was a very reputable journal, but one I did not publish in and to whose community of authors/readers I did not feel I belonged.  (One would be right in asking why I was ever approached and I don't have an answer.)  The other case is closer to the email you received.  It was an Open Access journal and I declined because that is not a publishing model I support.
I believe that setting all practical considerations aside (whether one has time,...) the litmus test is whether one would be willing to publish in that journal.  If the answer is negative, I think that you should decline.
