If you sell a product that does not live up to its claims, even if that product was manufactured by another company, there will be customers who take legal aim at you. A disclaimer statement is your best defense against such claims. For instance, a disclaimer might say the following:

"…(company) does not necessarily endorse, support, sanction, encourage, verify or agree with the content, comments, opinions or statements hosted by (company) customers, banner exchange participants, advertisers, vendors or partners. Information, products, and services offered, sold or placed online belong to the respective companies or individuals who place them there and are not representative of (company)."

The statement further makes clear that it is up to the consumer to assume the responsibilities attendant to buying a legal product. It is sad that this type action is necessary, but given the willingness of people to sue over virtually anything, a little time spent crafting such a clause can prevent you from losing money to specious claims.