Ouch! That's horrible. You made me look it up. http://www.facebook.com/ad_guidelines.php
It seems like in section 14, Downloads, they're against malicious downloads. Did they accuse your software of being malware, or did they straight up say NO software?
It seems my information was out of date. They used to have a total prohibition on it: "No ad is permitted to contain or link, whether directly or indirectly, to a site that contains software downloads, freeware, or shareware."
