struggling with ethical dilemnas

I find myself in an interesting situation this morning: considering the ethics of what I do.  Much of the time my work is with vulnerable populations.  However, the majority of my research participants self-disclose online, which means that they have already agreed to divulge information about their personal experiences.  That being said, I find rich information, regarding experiences of people involved in traumatic situations, in my face-to-face life as well.  The challenge is: how much of their information can I disclose?  Obviously, I would leave out identifying information unless I had their explicit permission to do so.  However, is it ethical for me to quote them without permission?  My conclusion, influenced by the advice of a colleague, is to hold off on sharing information privately disclosed prior to gaining permission.  The challenge, then, is how do you ask someone who is maybe not as familiar with blogging, if you can quote them on your blog.  This, I feel, is relevant to my research because my particpant bloggers are divulging sensitive information and should they divulge information regarding others in their blog without permission, am I being unethical including it in my research?