Other than the fact that you’re giving people your legal name and all of the details of your flight, there’s another reason not to post this info online. Your boarding pass contains a barcode or QR code that has all of your personal information for that flight encoded on it. Anyone with a decoder could use it to access that information.
Additionally, that barcode or QR code could contain a six-digit code called a passenger’s name record (PNR). This PNR code can give a hacker access to further personal information, allowing him or her to steal frequent flier miles, change your seat assignment, change your contact information or even change or cancel your flight reservation. If you keep credit card information stored in your airline frequent flier account, they could steal that, too. In short, it’s a bad idea.
It’s best to shred or destroy your boarding pass and luggage claim tags after your trip so that information can’t fall into the wrong hands.