Every now and then appears someone with the "new" idea of tainting coins. It's a very bad idea for multiple reasons. God, use the search button and you'll find a lot of threads about tainting.
What we need is an add-on for the Satoshi client and for the usual mining software to allow people melt-mining coins. That way we prevent the next "visionary" to taint our coins.
Melt-mining: mine a block and add a selfmadetransaction with all the coins you want to "melt" as fees. You need a tweaked client that prevents the selmadetransaction to be broadcasted but in your brand new mined block.
BITCOINS MUST BE FUNGIBLE.
Thank you. Taint was the word I was looking for.
Bank notes being traceable is one of the problems with them. When you use cash it is supposed to not be traceable. Using bitcoins should be just like using cash anonymously, at least as much as possible.
With the blockchain structure, bitcoins are actually LESS anonymous than cash. Even you may launder your coins, every single satoshi is still traceable to its generation block (or people can print bitcoin out of thin air). You can't just close your eyes and ignore the blockchain and say bitcoin is not (or should not be) traceable.
If you want increased anonymity, there are some proposal like automatic coin mixing. But that is your own choice.