Thanks for your comment ScottWhigham. If you've sold stuff on Craigslist/eBay, you would definitely know the value of such a service. The number of robo calls you get when you post your real phone number in ads is annoying. It doesn't end there - even weeks/months after your ad has expired and disappeared from Craigslist, you continue to receive marketing calls you didn't ask for and aren't interested in.
There is a reason why most people opt to use the anonymous email address that Craigslist provides while posting ads. We're only making it possible for people to have a similar experience with their phone numbers.