Mandatory 2 factor authentication for online banking is by-far the worst impact a law has had on my everyday-life in quite some time, while actually decreasing security, since more people will change to mobile-tan for the (now necessary) convenience of not having to fiddle around with a proper tan generator every time they check their account balance. First-world-problems, I know.
It actually makes more sense for PayPal to implement this, than it does for a regular bank. You don't need to authenticate individual transactions on PayPal, therefore the login itself needs to be secure. On the other hand, what is a hacker going to do after he logged into an online-banking portal? He can't do more than access the account balance and transaction history without needing a TAN.