[bduerst]

I've seen some rumors about blacklists, but I didn't think anyone took it seriously. All it would take is one exchange to allow the bitcoins to change addresses to defeat the purpose.

The international scope of the exchanges and their competitive nature makes it seem unlikely that blacklists will be successful. Addresses are pretty ubiquitous by design, so short of blacklisting entire exchanges I don't see it working. (Even then tumbling would get around it)