Should I worry about the data being overwritten by other information?
The answer would depend on what type of tag you were talking about and what kind of data was on the tag. RFID tags usually have a serial number that never changes. That number is associated with an object so that it can be tracked. There are often additional memory banks that can be written to.
In some cases, data may be overwritten. For example, you might overwrite information to indicate the station at which a tagged piece of work-in-process (WIP) was located. Each time the WIP moved to a new session, the RFID reader at that station would overwrite the number of the last station with a new number. This is not a very common way of using RFID transponders, however.
With passive UHF tags based on the ISO 18000-6C standard, users can lock memory so that it can only be overwritten if you were to send a passcode to unlock the memory. These tags also have memory that can be locked permanently. So, for example, you might write the date on which a drug was manufactured, as well as when it will expire and should no longer be used, and then lock it permanently. That way, anyone reading the tag could obtain accurate information.
—Mark Roberti, Founder and Editor, RFID Journal