Craigslist has a really bad history of abusing its users. For instance, a few years back they changed the TOS so that CL becomes the copyright holder of all ads placed on the site.
(a) A transfer of copyright ownership, other than by operation of law, is not valid unless an instrument of conveyance, or a note or memorandum of the transfer, is in writing and signed by the owner of the rights conveyed or such owner's duly authorized agent.[1]