If you update a Subscription product price from $100 to $120, all those Subscriptions created at $100 are not updated to $120. You have to manually go to EACH subscription and update the price which is very time consuming when you have hundreds or thousands of subscriptions. There should be a bulk way to update all subscriptions pricing without having to go one-by-one through each active subscription.
When it comes to fraud, the biggest threat you have to watch out for is chargebacks. After all, most people pay online using their credit cards, either directly or through a payment processor such as PayPal. If a credit card is stolen, its owner can usually reverse unintended payments. However, some people also do this on purpose to avoid paying for their purchases.