Is emailing potential Yahoo! Answers contacts a good, polite thing to do?

Of course it is polite to e-mail potential contacts. On the other hand, there are users like myself, who don't allow e-mail contact. If you hover over a user's avatar who doesn't allow mail contact and you see a link which says "add to my contacts", you should feel free to click on it, because for that link to appear, the user has marked his settings accordingly...:-)