The term “dirty bit” is a reference to the fact that even virtual goods can be tainted by their association with human and environmental degradation. But “dirty bit” is also a term of art in computer science. A dirty bit is a bit that is associated with a block of computer memory and indicates whether or not the corresponding block of memory has been modified. Dirty bits are used to “mark segments of data that need to be processed or have yet to be processed.” This double meaning seems to me to be significant, and I am working on ways to draw out the analogy. Suggestions welcome.