Wiki: How to Contact a Wiki Author or Contributor

Unless someone has listed an e-mail address in their profile, there is no direct way to contact them. By default, the email address you supply when signing up is not visible.

How to make it easier for people to contact you?

Put information on how to contact you in your profile: email, website, social media or other means.
To edit your profile, see http://social.technet.microsoft.com/wiki/contents/articles/149.wiki-all-things-profile-en-us.aspx
Check the "Email me updates to this page" checkbox when creating or editing an article. If you have not provided other info, this is typically the only way others will try to contact you. If you have a User Page - consider adding a "If you need to contact me, just leave a comment on this page" note to it.

How to contact another community member?

Check their profile. People who want to be contacted will often provide information there: email, website or social media. Many websites and blogs have contact information, and you can try contacting them through Facebook, Twitter, or LinkedIn (if they provide a link).
If the person is a Microsoft employee, you might check if the person has a blog. If they have an MSDN/TechNet blog, then there's a link on their blog with an email form where you can send a message to their email.
Comment on their articles. Many contributors subscribe to get notification of changes/comments to articles they wrote. Make sure you provide information on how to get back to you!
If the person's a Microsoft employee or if they frequent Ed's blogs, Wiki articles, or forums, you can just ask Ed. He might know how to get you in touch with them. (Ed will need a full name, and a role and group helps. He might not be able to contact the person because they might have left, they might not respond, or because their profile name might not match their real name.) Leave a comment on this article or email Ed... edprice at Microsoft.