Merchant of Venice replaces a Great Merchant for them, so you can have as many as you can generate from pumping out Great People. They get three free ones pretty fast if you go Liberty - one at Optics, one for Collective Rule policy and another for finishing Liberty.Oooh, but don't they only get two merchants of Venice? One in a certain era and one from the liberty tree? Not sure though, when I played Venice I wasn't generating great people all that fast and fell to Genghis & Hitler pretty quickly.