I have a Facebook account. Under their Terms of Use, the following constitutes “prohibited conduct”:

By using or accessing the Facebook Service, you represent, warrant and agree that you will not:

do anything that could disable, overburden or impair the proper working of the Facebook Service;
use any robot, spider, scraper or other automated means to access the Facebook Service;
send spam or any other unauthorized advertisements or solicitations through or using the Facebook Service;
harvest, collect or use addresses, phone numbers or email addresses or other contact information (collectively “Contact Information”) of users of the Facebook Service without consent from such users;
solicit private information (including social security numbers, credit card numbers and passwords) from users of the Facebook Service;
provide any false personal information in your profile, create more than one profile, transfer your profile, create a profile for anyone other than yourself or create a page without authorization;
use your profile (as opposed to a Page) for any commercial purpose;
offer any contest, sweepstakes, coupon or other promotion through the Facebook Service without our prior written consent;
use an iFrame or offer web search functionality on the Facebook Service;
intimidate or harass any user;
do anything that is illegal, infringing, fraudulent, malicious or could expose Facebook or the Facebook Service users to harm or liability; or
attempt, encourage or facilitate any of the above.

RS is potentially guilty of the bolded item above if he undertakes a concerted campaign to get Cato’s Facebook account revoked, based upon an unwarranted and unsubstantiated allegation.

However, the concept of “defamation” is conspicuously absent from this list of prohibited conduct.