Based on the rule here, it says "5 or more" ... I am in a game right now that the opponent has a chance to place 6 in a row ... but he/she hasn't do it yet ...
(hide) If you only look at some of the discussion boards on a regular basis you can add them to your favourite boards list by going to the Board page and clicking "Add to my favourite boards". (pauloaguia) (show all tips)