During Kevin Mitnick's talk, he demonstrated how to unblock CallerID. He announced his phone number, put his iPhone on the big screen, and asked the audience to call him with a blocked number. Being a hacker conference, not many were willing to risk disclosing their number on the big screen to the 800+ people watching. After a long 20 seconds one guy called and sure enough his number showed up.
After some really quick mental risk assessment, I decided to call too, since my number is also blocked and I was curious. Sure enough, my number also showed up on the big screen. (I quickly hung up hoping to prevent anyone from writing it down. No prank calls yet, *knock on wood*.) I added Kevin Mitnick to my phone's contacts list and it's really weird seeing his name in my call history.