ZERO ACCOUNTABILITY..
These are true of craigslist. However, using paypal provides much of this. The only information at risk is ones email adress. Paypal has a contesting system and, because of the assumed emails that will be sent back and forth outlaying the agreement, an individual should be able to prove if they are scamed.
As far as validation of skills go...well its the internet. Forgive the childish example: If I open up a website that says I am the King of Norway and vacation on Mars...this doesn't offer any validation. With essay writing references are unlikely.
All other forms of "safety" are really up to the wisdom of the user. A craigslist scammer is no different than any other online scammer.