No. Email does a better job. I don't want to have yet another medium to check and use.
Being a startup site, where people may be looking for contacts, co-founders, advice, etc, I think having a tool to get in touch with each other would be very useful. I vote yes do it, but KISS.
The person's website though would be something I would visit, and most people don't hide their websites on blogs.
EDIT: I should clarify: When a person writes a comment, it's the comment itself that would lead me to wonder what this person is all about. I'll click on his name. I'm not interested in a "profile", I'm expecting a website. The fact that I get the YC profile means I stop looking, and go back to reading the article. As such I never really figure out who the person is.
Many times I'd rather call someone up, but I may only have their email. Point is, there are usually always better alternatives. However, choices make the end goal more possible than it might have been.
The free text box in the profile lets the user give an email address, or their home page, or anything else including their phone number. The point is, they can limit how you can contact them. I don't think adding private messages on news.yc helps.