As for the userbase statement, I'll bet you 5 BTC that if a poll were made in the general bitcoin forums about the motives driving individual interest in the bitcoin movement, the individuals interested in Bitcoins for black transactions would be outnumbered by the users interested in Bitcoins for either personal profit or ideological reasons by at least 3 to 1. This thread sees a tremendous disparity of idealogy in favor of the black market simply because it is a thread about the black market Bitcoin economy, which uninterested parties aren't even going to take the time to read, much less post in.
That's irrelevant. I am not talking about these forums (how long do we really think all bitcoin users will be posting on these forums) but about potential for growth in the next 1-5 years. There IS a huge potential for BTC to be taken up to facilitate black/grey transactions, not as much other transactions (barring some huge collapse of some fiat currency).
But this whole discussion is irrelevant since I haven't heard any viable proposal of regulating bitcoins. You don't think a similar unregulated currency would pop up within a week? Even with internet gambling, the only reason it was able be regulated was because there were bank accounts to freeze. (Even there, arguably the bigger deal was that there was an incredible amount of money laundering going on, to the extent of actually buying banks to facilitate online poker transactions in the US).
Even if you do not accept my assertion, that as distasteful as it may be for some, black markets represent the greatest uptake potential of BTC (and not just drugs, but paying informants, bribes, weapons dealing, and prob even more unsavory market deals etc etc) there is simply no way to work around it.
and I don't nec think BTC will INCREASE this actual activity, it will just shift from cash and other payment methods towards BTC. In fact for some activities, it is likely to decrease overall levels of violence, etc just as any de facto decriminalization of an activity tends to.
If gov't really wants to capitalize on this, then will regulate and tax drugs and make it EASIER to buy drugs with your credit card at your local corner store much the way itunes has capitalized on music even in the realm of easy digital piracy.