This is just fear and noise because you are afraid of the ramifications. Any service could be as customizeable as you want. You want to only check relationship to famous addresses: Bitstamp address for example, then you could do it.
I see cash transactions all the time that do not happen because the person with the cash is a drug dealer. It happens.
Why only famous services? For this to work, you would need everyone to agree with this.
Also, how do you know that person is a drug dealer? Did you check the banknote serial numbers in a database?
I am talking about a service for one person not everyone. I ask for someone's originating address, i type it into my dirty coin checker. I can choose to do business or not based on the results.
But WHAT constitutes 'dirty'? What's 'dirty' for one individual may not be for the next (think global transfer). Boycott the vendor not the coins.
The only one that's gonna create such an app for you is the gov't...
Do you not realize that the right to freely trade is a basic human right?
I already said as a global mining or payment option checking for dirty coins is fraught with issues. However, for me it would be a nice service I would want, especially when buying on localbitcoins. Before i meet with the guy I will ask for an address for proof of funds. I will check his address to see what the dirty factor is, I can choose to skip meeting him if i want.
Will also be a nice way to avoid getting shot and killed by the Bitstamp thief.
The right to freely trade is a basic right, as is the right to refuse!!! It is a fact of life that some people cannot do basic transactions in life because they have violated the trust of people or society, it is just the way it is.
I think it would also be a cool app to see how dirty your own coins are.