LIke I said in the OP there will come a day when a new user will buy bitcoins (say locally for cash) and when he goes to use them at a business or exchange or where ever they will be rejected. Not 100% of the time...but it will happen and we all know how the media today loves to jump on anything bitcoin related that is negative.
For the millionth time this is only true if you choose to do business with a company who does not actually accept bitcoin but fiat. If you happen to transact with a user or a company in a peer-to-peer manner on the Bitcoin network there will never be such a thing as "transaction rejected".
The fact that people will have to worry about which merchants will accepted all btc and which may reject btc based on some list is not a good thing for encouraging mass adoption.
If BTC was perfectly fungible this concern would not exist.
If merchants support such a blacklist then it's likely they are not actually using or accepting BTC.
Bitcoin is perfectly fungible, the government though would like you to believe otherwise.