In the near future, the vast majority of bitcoins in circulation will be considered "tainted". We could somehow compare this with the banknotes contaminated with cocaine that are now in circulation in the hands of people who have nothing to do with it (
Contaminated currency).
It's even worse than that for bitcoin. If I hand over five $10 bills and one is "tainted", then the recipient receives four "clean" bills and one "tainted" bill. If I pay five 0.01 BTC inputs and one is "tainted", then the recipient receives one "tainted" 0.05 BTC output. For this reason, as you say, almost every bitcoin in active circulation can be deemed to be "tainted" in one way or another.
6 transactions for a company, 12 for a government.
Which, just like the example above, makes it completely arbitrary. Let's say I have some bitcoin which are a result of illegal money laundering. I could perform an honest trade with an honest user, and now they have tainted bitcoin in their possession despite doing nothing illegal. On the other hand, I could bounce these coins around between my own addresses 12 times and now they are clean again?
The whole "tainted" bitcoin thing is a scam invented by governments to exercise control over us. We shouldn't accept it.