A new idea in modern times on advertisements, on the metro especially, is to provide a QR code for the potential customer to scan. Have your even seen anyone scan one? No, I didn't think so. The advertiser has stacked several things against himself: 1) the potential customer must have has phone or similar device on him, 2) this device must a camera, 3) it must have software on it that can be used to scan and decode QR codes, 4) the potential customer know how to use it, 5) he musts unlock his phone (this can be particularly burdensome if he uses a proper password, which some companies actually require from the employees on the company phone), 6) the potential customer must be close enough to scan it or walk up to it, and 7) the potential customer must not be embarrassed to do so. This could all be fixed by the advertiser adding a short, memorable URL code, that is readable from a distance, under the QR-code, but this is exceptionally rare, and the advertiser instead solely rely on what is the current fashion. This is particularly problematic when conduction research as it with filter out anyone that is not able or motivated to scan the QR code.