I got my Sipura yesterday and spent the evening configuring it and my Asterisk server. I was in a high-fiving mood once I heard it ring. Woot!
One cool thing I experimented with was the ability to set the outgoing CallerID to anything I want. In essence, you can fake a call from anywhere. I assume it works for *69, too, meaning those prank calls just became much more fun.
On Metafilter today, I found a company that haqs found an interesting use for this, um “flexible” CallerID stuff. Dial-A-Cheater fakes a call from your suspected home-wrecker, allowing you to see how your significant-other reacts.