Observers and measurements in noncommutative spacetimes

We propose a `Copenhagen interpretation' for spacetime noncommutativity. The goal is to be able to predict results of simple experiments involving signal propagation directly from commutation relations. A model predicting an energy dependence of the speed of photons of the order E/EPlanck is discussed in detail. Such effects will be detectable by the GLAST telescope, to be launched in 2006.