the word taint is actually better then the word marked.
taint is about it containing traces of something which over time can reduce in levels
taint (teɪnt)
n.
1. a trace of something bad or offensive.
2. a trace of infection or contamination.
v.t.
3. to modify by a trace of something bad or offensive.
4. to infect or contaminate.
5. to sully or tarnish (a person's name, reputation, etc.).
v.i.
6. to become tainted; spoil.
if we say its marked then that applies a more permanent status that the coin is forever marked at a single level that cannot change. meaning each time a bitcoin is used it will be flagged up as bad funds, whether its passed 1 hand or 500 hands.
if we say its contaminated then that applies that bitcoins on a physical level have been altered/damaged/changed in a negative manner. which we all know bitcoins are not physical. meaning that people will not want to touch it. at all.
taint is more appropriate as the level of negative trace reduces with each transaction, thus allowing for judgement that the receiver directly knows the negative trace (high taint) or has no knowledge or connection to the negative trace (low taint).
unlike bank notes, which after being in circulation for a few years, get burnt by banks and new notes are produced to replace them, bitcoins can not get deleted and replaced with fresh bitcoins, over time every coin will have some taint of some sort. so i would never want to use the term marked as every bitcoin will get flagged up everytime its used. the same with contaminated, every bitcoin will get flagged or people will not desire to touch them, making bitcoin theoretically useless. but the word taint allows for people to realise that in the real world if something changes enough hands its bound to get dirty, but atleast they can tell how dirty it is to accept it or not.
