There are plenty of fraud measures that can take time to complete; it depends on the order too. For a $400+ order/month we call the credit card company to confirm the order is indeed legitimate and may speak to the customer briefly if concerns arise. If the transaction is deemed high-risk, it may also be necessary to get photo ID.
Its better to spend 24 hours and insure the order is legitimate than to accidently host a spammer, phisher, or child pornographer. Perhaps that's just my mindset, and I'm sure existing and potential customers wouldn't want to be on a network that takes risks / slacks when it comes to fraud.