Short Answer: No.
Long Answer: The point of having an email field in a comment form is to have a way for the site owner to contact the commenter. I do not believe that field is necessary and adds unnecessary complexity to your form. Complexity discourages people from commenting and in turn weakens your blog community.
Real life example: Imagine you are giving a keynote. After your talk, you strike up conversations with audience members. They compliment you, ask you questions, and suggest alternatives to what you said. All of these are real world comments, but you’re not asking for any email address. At the most, you’ll ask their name to keep in touch.
That same practice should carry over to the blog world. People’s names and comments are most important to the discussion. If the person wants to be contacted, they can leave a link to one of their sites.
Spencer Fry eliminating one field form his comment form encourages readers to leave a comment.
Always keep your fields down to the bare minimum. Only include basic fundamental fields to ease the burden on your users.
Update: What’s worse than asking for your email when you want to comment?
Answer: Having an email field and a CAPTCHA. This is from a user experience blog nonetheless, the last place I'd expect to see one.
Am I missing something here? Cause in this actual form I get asked my email. Do you mean it should not be mandatory, or not be asked at all?
I do ask for it, but it is not required.
I ask for it only because of the “Subscribe to all the comments via email” checkbox for people to stay up to date on this post. You can comment with your email and get updated, or you can comment with just your name and comment.
So if we don’t have subscribing option then we should not ask for commenter’s email