Promo abuse: How Paypal was forced to close 4.5 million accounts

I have recently read some news on Bloomberg about how Paypal had to close 4.5 million accounts and how its shares then fell by the most on record with a loss of over 25% of its company value on the 1st of February. In this article I will share my thoughts on why that happened and some ideas on how to help prevent promo fraud and abuse.