The Verified Member thing is an attempt by ECF to reduce scammers on the classifieds. Nothing's perfect, but it is a decent try.
Basically, there's a Paypal verification path, an E-Bay verification path, and a Vouched For By Verified Members path. The first two methods means that an outside organization has checked you out, you have provided them real banking and/or credit card info so that if a Sale does go awry there is a "real" Seller who the Buyer can follow a complaint path on.
The last method means there are at least 3 already Verified members willing to step up and say they vouch for you, they know you well enough (not necessarily through Classifieds, but through interaction with you here on ECF) to believe you are a good egg, not likely to be a scammer. You shouldn't Vouch for another person "easily", you should have enough interaction to be pretty comfortable that you have a reading on the other person. It's subjective, but an honest attempt to provide an "out" for the people here who are active on ECF but don't have paypal or EBay verification methods available.