It is a worrying possibility, because, outlawing bitcoins to business would simply make it too risky (or apparently risky) to accept bitcoins even if it's hard to enforce it.
And I also believe it is not that hard to enforce it. Undercover agents of governments could simply pretend to buy stuff with bitcoins and then if he closes a deal he can arrest the person with a lot of evidence and testimony against the bitcoin receptor.
I believe bitcoins would become more usable only in a situation where the current currencies are in collapse and governments have little control of law enforcement. In a crisis environment only, which bitcoin could help to end, and only then, be stablished as a widly accepted currency.