Now bio-weapons can have bacteria with "**** you" embedded in their DNA. Sounds interesting. And would be very useful for tracking strains etc. Evolution would eventually corrupt the data, but with the many copies present in many bacteria, it should be safe for the next 100 or so years.
That's the whole point... I would have thought that you can't be sure of this. Some bacteria have been stable for millennia, others such as the mutate continually.