I'm firmly in the members only camp
We can prevent most flames, irritating advertisements, and other forms of aggravation by allowing only members to psot. I think it would also make life far easier for the administrators and moderators. Keith, Aaron, etc don't need a bunch of extra work and we can keep it to a minimum by allowing posting only by registered members. Registration is a rite of passage and I don't particularly like having folks use only "handles" to identify themselves. There is also the advantage of having a little knolwdge about the psoter by looking at their info in the left column or by going to the member section and looking them up. This advantage also accrues to the person posting since responses can be tailored to their location, age, and their particular interests.