Continuing my discussion...

#1. security; the problem I suggest isn't security with the bitcoin network.  It's YOUR security.  Real world bad guys can see YOUR bitcoin balance worthy of their efforts; starts cutting off your fingers and flesh until you transfer your funds.  You didn't need those arms nor legs anyway.  We'll call you Stumpy.  CURRENTLY in the real world; why aren't you walking around the streets with wads of money hanging out your pockets?  This is exactly what you are doing with bitcoin.  Once you are personally connected to a wallet (all it takes is one stupid mistake), there is no safe/secure way to completely hide again.  I think you an idiot if you believe you can receive/send payments without anybody knowing who you are.  Anonymous payments in and out?  Really?  Real world doesn't work that way.  Even criminals can't pull that off.  YOU are not good enough to never make a mistake.

#2. fungible. I deem you an idiot if you think bitcoin is really fungible.  The CURRENT network mostly treats bitcoin as  fungible.  But this is changing, and, "tainted" coins and wallets in the future will be treated differently, especially at OFF-RAMPS.  Example; you being a naive idiot thinking your bitcoins are fully fungible; you then pay them to somebody and they are CONFISCATED.  Ha ha, jokes on you.  I'm sure there will be plenty of good excuses for confiscating your coins.  You never really know if your coins will be confiscated until AFTER you send them.

I'm hoping somebody makes a bitcoin PRIVACY hard fork; sooner than later.  Afterward, the market will figure out the rest.