Clearly, when a service provider like Facebook adds this functionality to its service, then it is going to have an impact in usability. (See Facebook Kicks Off Implementation Of QR Codes)
According to the Techcrunch report then there are two types of QR codes:
a personal barcode which would (I assume) return a basic profile + link to your profile
“status QR barcode”. which would (I assume) return your current status when read.