Now there are hundreds of domains out there, requiring each admin of EasySocial to maintain their own list of valid domain extensions is not practicable. Also the list really serves no purpose as someone currently could try to post a valid url link but have it rejected if not on the list, but also they could post a url that is in the list but actually doesn't point to any content yet EasySocial will accept that!
Perhaps better is to allow users to post any url and then have an option to turn on url checking (this setting actually exists but currently doesn't work!) Then also maybe replace the list of top level domains with a 'blacklist' that admins can use to disallow links to certain sites.