Not surprised at all. We got banned too without any warning a few years ago. I wrote about my story here: https://news.ycombinator.com/item?id=11944701
Lots of people would simply think "It won't happen to me" and move on. But this is just another example that if it can happen to people using Paypal for years, it can happen to you too. It's better to offer other payment channels to customers so you can diversify. And if possible, move away from Paypal entirely.