The text message was a phish, leading the guy to a login page that WASN'T Craigslist. It's a scam to try to con people into giving up their usernames and passwords. What this guy did was write a short program to spam it with 1000 fake email addresses and passwords. The theory is that if anyone did fall for it, maybe the scammer won't be able to find the real stuff from the crud that's just been dumped in there. It was a bit crude, but not bad for 5 minutes of vigilantism against a scammer.