Standard barcodes have too much detail to be recognized by Microsoft Pixelsense. You will need an external device to read them. From the Tagged objects for ms surface 2.0 whitepaper
Barcode Support
A barcode is an optical machine-readable representation of data typically used for scanning products or tracking inventory. The most common barcode is the UPC code used for scanning products at point of sale terminals. The best barcode integration for Surface uses a dedicated external barcode scanning device that can be built into the Surface enclosure, connecting to the unit via USB. Surface does not support displaying barcodes for scanning by external devices.