Radio Frequency Identification (RFID) has recently received
a lot of attention as an augmentation technology in the ubiquitous computing
domain. In this paper we present various sources of error in passive
RFID systems, which can make the reliable operation of RFID augmented
applications a challenge. To illustrate these sources of error, we
equipped playing cards with RFID tags and measured the performance
of the RFID system during the different stages of a typical card game.
The paper also shows how appropriate system design can help to deal
with the imperfections associated with RFID.