Yes and no. Like anything else, you have to be careful. I have found excellent people through Craigslist- but you have to screen them.
In my case I live in a university town, so there are many university people looking for rooms. It is a simple matter of checking the student/faculty directory.
At the same time, I have found people who had arrest records, drug convictions, even a registered sex offender. These were revealed by a simple background check, which should always be part of the process.
Craigslist is not as effective as it was in the past. so I use other sites as well. Zumper, for instance, which automatically posts also to Padmapper and Facebook and has an option for screening applicants.