Should you have more than one account, no more than one account may be connected to a Facebook account, and the accounts may in no way interact with one another.
Interactions include, but are not limited to:
Being friends or linked in anyway
Sending gifts, supplies, or transferring items in any way
Being a part of the same team
Joining the same tournament or any sort of competition, even on different teams, or a part of different groups
Knowingly purchasing a marketplace posting which was posted by another account in their control
Contributing towards a shared, or global goal
Note that the above list is not an exhaustive list of all possible interactions and that it is up to the sole discretion of the game's administrators to determine if two accounts controlled by the same person have interacted.