It seems to be tainted with coins from Mt Gox. It could be some of the stolen BTC, though even if it is I doubt the current owner has any idea.
There is no such thing as 'taint'. A bitcoin is a bitcoin. No matter if it was just used to kill the president of Laos. The notion that bitcoins get dirty and less good based upon their prior use - is completely silly. When someone hands me a 100Euro note - I don't give a damn what nefarious transaction it was used for last week. That 100 note looks the same amount of green to me.