I've tried it before, it didn't really seem to do much. Maybe I wasn't going about it the right way, but I'd advise against it.
There are a few reasons why this is generally a bad idea. Reason #1 is Craigslist is very proactive in stopping this from happening. They will file lawsuits in the drop of a hat, and usually only give you one warning. They pursue legal action fairly diligently. Aside from that I think it's probably a waste of time for you. Most people sniff out an ad a mile away and ignore it. Then those who don't ignore it are probably just curious and most likely not the highest converting people. Remember they went to craigslist to look at ads, not find new websites. I would say your time and effort could be better spent elsewhere.