We do not check credentials at the door.
Even had we had wanted to, such a policy would go against how the Stack Exchange network of sites is designed; we don't rely on a particular level of education or certification to judge the correctness of an answer, we rely on the fact that enough people are knowledgeable enough to recognize a good answer from a bad answer, and to vote accordingly.
Right now, that model is still in development, which is one major reason the site is still in beta. So while your concern may have some merit at this point in time, it is (God willing) only a temporary concern. Once we have developed a strong core of users, good answers will naturally rise and bad answers will naturally fall.
A correct answer remains correct regardless of who it comes from, and a harmful answer remains harmful. Judge the post, not the poster.
Our priority at this stage is to build up an active community of knowledgeable users. It is not, nor should it be, our responsibility to "dumb down" all of our answers so people new to Islam don't get confused. There will never be a shortage of new users to ask new questions; attracting experts and getting them to stay is the difficult part, and that is the part that will make us stand out and excel as a repository of Islamic information.
As far as I'm concerned, any policy which treats our users as if they don't know enough to answer questions flies directly in the face of that. If the only people we welcome are those who cut-and-paste answers from IslamQA, that's exactly the site we're going to get.
And if that's the site we want, well, there's already IslamQA for that.
That said, it is important to note that this is a non-denominational site. There are many reputable scholars who do not agree with the majority view — even the traditional Sunni madhabs disagree with each other on many issues — and we as a site do not forward any particular flavor of Islam. There are many Muslims who follow these scholars, or the interpretations they posit; their questions, and answers, are just as welcome here as those of the majority.
This is very important to recognize when asking a question, otherwise one is likely to solicit opinions from across the board. If the questioner wants an answer to be in accordance to the majority view, or to only quote reputable scholars, this must be made clear in the question. If the questioner only wants evidences based on the primary sources, rather than quoting scholarly opinions, again this must be made clear in the question.
That way, any answers which do not give the questioner what he asks for can be downvoted and/or deleted.