Services like the new Star38 Caller ID spoofing service mean it’s only a matter of time until we get to spam-style formal whitelists and blacklists for phones — especially for VoIP devices.
After all, if Star38 is going to circumnavigate Caller ID by using junk phone numbers, then call recipients will almost certainly respond by blocking all numbers except for the ones they know and trust. At the same time, as we migrate toward VoIP, you can expect to see shared network-based blacklists that are rapidly updated to include the junk numbers used by services like Star38.
[Update 9/3/2004] It seems that Star38′s founder, Jason Jepson, is having a change of heart. According to the NY Times tonight, he is receiving threats and now wants to sell the Star38 service, despite having spent, ahem, $3,000 developing the thing.