PrismAIO now supports FLX accounts to be used on US Footsites. Accounts are not required to checkout on Footsites but do provide some benefits. Here are the positives of using accounts:
Free shipping for FLX account members
Ability to accumulate points in your FLX account which can later be used for in-store reservation boosts etc
Less likely to trigger Payment Verification emails (unconfirmed)
It is important to note that you can only use ONE ACCOUNT PER TASK! If you use the same account across multiple tasks, the account will be disabled permanently.