Facebook has taken a stand on just what you can or cannot show in an ad on the social media service. Of course, their decision came a week after said ad was running. As a result, st least a short while it was OK for Facebook to take the money of the Just Say Now organization before it extinguished the campaign. The LA Times reports Pot leaves are easy to find on Facebook pages. But the nation's largest social-networking site has decided they cannot appear in advertisements,