Making farms unlimited will raise the value of farms, this is a good thing. This makes destroying farms more worthwhile. For farms you'll need lots and lots of space, so you won't be able to defend all of them adequately, allowing raid tactics to really injure an economy. The bad consequence is, as stated before, that you get an infinite resource, which is not immediately something I dislike, but what I do dislike is a static infinite resource (dynamic: eg. tree growth, dynamic animal populations; static: eg. fish in AoM, infinite farms)