Stack Overflow is a great tool for programmers, and I can definitely see the potential for using the same format towards Spanish.
Having said that, I see some deficiencies compared to the traditional go to: WordReference Forums.
Based on my first impressions, there isn't really any culture of correcting bad Spanish. When I say this, I mean not only in regards to the actual question being asked, but bad Spanish being used in the comments, or that has been used to provide context/more information for the question.
Although WordReference has no mechanism to reward posters for correcting people, it is usually a given that members will correct bad Spanish when possible.
I think Spanish Stack Exchange can improve upon this by directly rewarding members for taking the initiative to correct bad Spanish.
This would not only lead to higher quality Spanish being used on the part of members overtime, but also remove any inhibitions not to do so out of fear of making (read: solidifying) mistakes and errors.
Otherwise, we are only encouraging people to ask in English(which I find counter-productive) or turning a blind-eye to bad Spanish being spoken (which I assumed was this site's goal to improve upon).