Steam already stated they’re limiting to 1 per household.

The longer timeframe also allows us to do some extra validation on the signups to make sure they’re real accounts, with only one per household. 

Limit one signup per household. We will use payment method, shipping address, and other information to eliminate multiple entries

the only part they can’t tell is gifting. i think they could fix that by requiring the account that would have to claim it during purchase. otherwise SN + account + location would pretty much end scalping. and if they enforce the one household the children can still have their games…