Is it secure to put a wallet address on one's business cards as a QR code?
that's not a bad idea in regards of doing business and distributing it to people. however, as far as I know, a single address is fine because the address itself is secured. the security flaw of a single address distributed will be - people can check the addresses on how good your business is doing. hehe. correct me if I'm wrong. Wishing you all the luck with your business.