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.
This is one of the worst ideas I have ever heard. It's so obvious that the miner and the owner of melt coin is the same person. Even worse, imagine that your block is orphaned. You "melting transaction" is now known to the whole world with 0-confirmation. I wish you could mine another block to include it before any other people did it.
In the last 2023 blocks, only 26 were orphaned. That's about 1,3% odds of loosing all the meltmined coins (to a lucky miner). I prefer a 1% chance of loosing the melted coins than your tainted coin system. Tainted coins will affect all the bitcoin economy badly but meltmining pools only have a 1% chance to loose the block. I insist, tainting coins is a very bad idea because it will hurt all the bitcoin economy and the solution is not so risky for a melting transaction.