Thanks for this thread GM et al.!

A couple issues perhaps you can help me with. 

1) Coinjoin as I see it adds some plausible deniability but the taint is still there.  Anonymity is probably not the right word.  If one of the input addresses is considered a red flag, all you've done at the end is generate a little extra work for researchers who now need to follow all the outputs to see who took the money.  As I understand it, the zerocoin protocol does no better.. and in fact to do better is impossible because if we can't follow the money, we don't know it's real.  Trustworthy private mixers on the other hand could offer some real anonymity.  To spell this out further, I have some coins at address 1A and I want them moved to address 1B with no public record of ever having been associated in any way with 1A.  Can coinjoin do that?  No. Can zerocoin?  No.  I guess this is what you meant by certain users able to pay for better anonymity will not bother with coinjoin. 

2) Dust payment deanonymization?  Huh?  All payments / TXs are already public.  How does adding a dust address to somebody's addy change anything?  This cannot be the motivation for a dust-to-old-addresses sender.  There is already a tag marking every address on the blockchain: the address.  I want to hear more about this "R" attack.