If you are in the business of selling domains, some feel it's not such a good idea to use privacy protection because you are making it a little more difficult for a potential buyer to contact you. Also if you are running an online business, hiding your whois information might indicate you have something to hide.
I would suggest putting a Google voice phone number in there, create an email address for domaining, and use a PO Box address. That way you are at least using a real physical mailing address someone can reach you at and you are doing more to reach out to your potential buyers while still maintaining your privacy. Lots of times those privacy protection services make it difficult even to send an email. The buyer would have to send an email, then the buyer gets a link via email with a form they fill out on a web page and then submit which then goes to your actual email address. Those extra steps could lead to a missed offer.