I like what Karin wrote about educating clients on the pros and cons of any given exercise program. A second step is educating clients on what qualifications to look for in their trainer and what types of classes to look for (i.e. is there a program for beginners or do they throw you in right away with experienced exercisers?).
Finally, I think it depends highly on the trainers at the Crossfit facility. I’ve known some very qualified Crossfit trainers who practice safe progressions for their new clients, including classes for different fitness and experience levels. I’ve also known some Crossfit instructors who I wouldn’t feel comfortable recommending.