Registration to a web site also aids in security. Though I have never had people register at my web sites I do insist people register for my forums. Asking for a person's telephone number doesn't do much for security unless you're accessing an international telephone database and checking authenticity, not likely. I'd suggest keeping the registration but drop some "very personal, unnecessary" information requests. If I were to register at a web site insisted on getting my phone number I'd leave. Listing your phone number should always be an "option" anyway.