Andrew, do you mean that somebody posted a question in G2G and you want to respond by private e-mail rather than answering in G2G? Assuming the poster was logged in and his/her name is displayed under the question, you can just click on the name. That will take you to the G2G profile, and at the top of that is a link to the person's profile. On that is the [send private message] link on the orange stripe showing him as profile manager.
