The problem with this is that Bitcoin is just about the least anonymous thing ever. It only seems anonymous because nobody's built the infrastructure to track it yet.

This statement is a bit hyperbolic. Bitcoin isn't as anonymous as say cash, but it's a lot more anonymous than most online payment methods (excluding a few altcoins which can really just be seen as innovations in the bitcoin/blockchain space).

Bitcoin will evolve to be exactly as fungible as is required to maintain its efficiency. As the cats build tracking tools, the mice will continue to expand on bitcoin's fungibility.

Tumblers..

I don't think that's really inherent value in the sense referenced. A commodity is something that satisfies wants and needs on its own. See, e.g.:

http://money.cnn.com/data/commodities/

The reason I think it matters is that when commodities are used as currencies (e.g., gold, silver), the use value supports the currency value. If gold's value as a currency falls to zero, you can still make some nice jewelery. Whereas if people stop accepting dollars or Bitcoins for things you actually want, then they are basically useless.