Sorry about that, Chief
I was reading the online rulebook and found the following rule under the "Place A Building Site" section on page 5.
You can not choose never have more building sites present on the main board than you have buildings left on your guild board.
I believe the intent of this rule is to prevent a player from placing, say, her 3rd Building Site on the map when she has already built 3 Buildings. But the rule has an extra word or two in it that messes up the meaning of the sentence.
Has this ever been clarified? Or does the rulebook that comes with the game have a correctly worded sentence?