Be very careful doing this w/ Craigslist. If you read the posting agreement there, you are agreeing not to spoof or impersonate another person and if you do you are agreeing to allow CL to pass on any and all identifying info to (that person) for the purpose of collecting damages, etc....
In other words, they do not have to use the courts to subpoena (your info), you have already agreed to hand it over.
Apparently this is a significant problem on the *free blowjobs* section of the site.