Efforts are being made to 'spread the word' (see here) thru bloggers and society mailing lists.
Unlike most of us currently participating this early in the beta, most genealogists I know don't come the tech community and are not that tech savvy. My admittedly unscientific sampling of a few members at a recent local genealogy meeting led me to believe there was a hesitancy that needed to be overcome before they would join and ask a question of their own, even though they all were passionate about genealogy, clearly had appropriate questions, and had done significant research of their own. My local society does not have a Q&A on their site (hopefully genealogy.se will obviate the need for one) but I have found answers to my research questions in another society's site that does have a Q&A site. This led me to wonder if we could increase our membership by helping those individuals who had unanswered questions on that site and others like it. If we answered a question they were interested in, they would be more likely to join in.
For example the Essex Society of Genealogists has their own Q&A with many unanswered questions. I think it's obvious that it's appropriate if asked by the person who had the original question. Is it appropriate for someone else to re-ask some of their questions on genealogy.se? If their question was answered, they would more likely to participate going forward. Conversely, the 'stand-in poster' would not have the context nor the passion for the original question, although stand-in could communicate with original ESOG poster and refer them to genealogy.se.
The questions on the ESOG site are obviously real questions that for the most part should be in-scope for genealogy.se. So the real question is whether it's appropriate for someone other than the ESOG poster to repeat the question on genealogy.se as part of the membership drive.