The amount of information they can hold is especially important in the case of bank transactions. Alipay and Wechat Pay (in China) have QR codes that change every minute. The merchant transaction has to be performed with the current QR code. It's basically a poor man's substitute for the encrypted handshake provided by contactless payment protocols. If someone got your payment QR code they could only abuse it for 1 minute.

I do dislike the use of QR codes for static data, such as a username on business cards and posters. From a design standpoint it looks horrible and busy. I wish those apps had the ability to recognize a logo instead. Or even just a UI to scan and OCR a text username on a business card.