Sadly a lot of people play fast and loose with their IP addresses being made public. It only needs them to meet someone with malicious intent to cause trouble.
The biggest culprit for exposing a person's IP address is Skype. I've learned recently that there is a website that as long as the Skype user is online, this website can reveal the persons IP address. Most (if not all) of these living gaming stream 'swattings' happen because the streamer talked to someone on skype at some point, or his skype name is known.
Thankfully this security hole in Skype is now becoming more widely known and people are preferring to use voice servers instead, hosted at a central location that doesn't give away a users IP address to others.