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.
thats only because you dont know what nefarious transaction have been done with that note.