If you say you don't care, then I think you are not being a responsible member of society. You should care and you it is easy to check, so why not do it.
No, it's not. After the thief uses a coin mixing service, there's no way to tell where those coins come from.
I didn't say he used a mixing service.
But I say he does. We need to take into account all scenarios.
So in your scenario my app to check address history wouldn't be useful because of the mixer. Yep great.
You seem to disregard this reason, when it's actually one of the strongest. Do you actually understand how mixers work?
I am not disregarding your reason, it is valid. But me rejecting an unmixed coin is just as valid.
I just read this article about a billioinaire says "So if someone offers you one of two bitcoin, you should choose the one that has never been attached to Silk Road or that has some dubious history."
http://venturebeat.com/2015/02/16/heres-why-bitcoin-will-be-bigger-than-the-internet/I think my little app that tells me how dirty your address is would be pretty useful, more confident than ever.
EDIT: seems billionaire didn't say the above