First off I want to say that Craig’s List is NOT a bad job board. However, simply by the nature of it’s structure, there are some problems with it as a job search tool.
The main problem is that it’s very easy for companies to hide their name. In fact, companies have to specifically list their company name in order for it to appear, Unlike most job boards, there is no “company name field” that needs to be filled out.
This is a big advantage for employers that don’t want to be pestered with phone calls, etc. when they post a job.
Also, the default anonymous email address is a godsend for employers.
The problem for job seekers is two fold.
1. The job seeker has no idea who the employer is. It could be some evil person in some 3rd world country trying to extract money from the job seeker’s bank account. I don’t think that happens very often because the Craig’s List people check out job postings. However, not knowing who the company is makes some job seekers reluctant to just blindly email the personal information required to get a job interview. Craig’s List is a great tool for accumulating resumes of job seekers for position that MAY be opening up. And it’s free in a lot of cities. So, the incentive is there to just go resume harvesting.
2. No replies – My brother was job hunting recently. He said he responded to about 50 job postings on Craig’s List. He receive maybe 2 replies. A lot of companies that don’t list their name feel that they don’t need to reply to job seekers. If they do reply, they risk having to receive follow-up emails, etc. Too bad for you Mr./Ms Job Seeker.
The advantage of using Craig’s List for job seekers is that it’s very easy to apply to job postings. You just email resume to the anonymous email address. Think of it as having a big handful of darts. If you through them at a dart board all at once, you just might get a bulls eye.
So, companies can use Craig’s List without accountability. They can post jobs that may or may not exist and no one will know. Job seekers are often times sending their resume to someone they don’t know.
I think Craig’s List should make some changes to increase the transparency of employer job postings. I’m quite certain they will get right on it! 
One final thought from an employers perspective. We posted a job on Craig’s List and received lots of resumes. However, only one was from a local person that matched the skills we were looking for. Also, I talked to another employer a while back. He stated that out of 25 applications, only 2 people actually sent complete resumes. These are indeed anecdotal examples. I’d like to hear if other employers experience similar results.
-Sam