I completely agree with you that Craig's List is a fantastic tool. In the past, Craig's List helped us find set pieces, build connections, and hire vendors. I just bought some cheap school desks via Craig's List for Ignite's next production. So, all theatres should seriously consider Craig's List a great resource.
The exception is the talent section. I am pleased we have found great artists like Adam. I posted a notice for a choreographer, and I recieved an excellent responses. For instance a professional burlesque choreographer with off-broadway experience sent an email, and I also heard from a visiting professor of dance at SMU.
Those are the success stories. Believe me, there is even more failure.
Most other people are just simply unprofessional. I don't consider anyone a viable candidate if they lack a strong letter of interest, a resume, or at least a website. One person responded to our Connections Project (Boston) post with "i am an actress." No real name...just an email...and that she acts... We all know the process when we're at an audition: dress in professional clothing that you can move in, and bring your resume and headshot. A professional first impression reflects your work ethic and seriousness, and I've only seen 3 good examples from Craig's List respondents.
I believe that the posts need to be professional, too. Most aren't. This is probably why it's a bigger risk for actors.
My time is never wasted because I benefit from having a large talent pool. An actor's time is wasted because you might be committing to 4 weeks of hell. This is slightly true of any job in this business, but the nature of Craig's List can make things worse.
Some posts just don't share enough about the theatre or production company. Here's an example of a company posting just the role requirements. The respondent knows nothing about this company's quality.
Professional theatres need to post on Craig's List. We may not get the most professional actors, but that's ok. We need to establish a presence. In my opinion, Backstage.com is the best resource for both parties, but theatre should be at the community level. (Plus a subscription to Backstage is pricey.) Perhaps the next step is to develop a Craig's List etiquette for audition notices. Otherwise, Craig's List will be where you hire porn stars...