I do not include my phone number or mailing address on my personal calling cards or website. The reasoning is as such:
If there is some reason you need to contact me by phone or postal mail, you should e-mail me to get this information (and to justify your need for said information).
If confidentiality is of the essence, you may wish to use my PGP key to encrypt your message, though you're encouraged to verify the trustworthiness of my key first, using your web of trust. You can also verify my key in person, but if I'm available to you in person anyway the whole PGP thing may not be necessary!