I'm not making a philosophical argument. It's a practical one. If tens of thousands of retailers are accepting bitcoins at their website, then the government is going to step in. There is plenty of history to support this. On the other hand, if tens of thousands of people are buying and holding bitcoins like they are beanie babies or gold coins, then you aren't likely to attract the attention of congress, yet you've met the goal of creating an alternate method for holding some of your wealth.
If the point of bitcoin is to make a stand against government invasion of our personal wealth, then bitcoin is on the right track. When/if retailers accept bitcoins you can bet the government will be there to regulate and tax them.
If Bitcoin ever takes off, it matters not what they are called or by whom. Eventually, any method of exchange that is difficult to track will get the attention of those who, for whatever reason, feel that it is thier duty to track. If retailers never accept Bitcoin, then there will never be a problem; but the acceptance of Bitcoin for trade is the root purpose. If retailers never accept Bitcoin, then it is a failure and whatever those other people do is irrelevent. Other attempts to develop an online currency such as this have failed because they all, ultimately, depended upon a single institution to support them. That institution became the single point of failure for that currency, and logically became the target of TPTB. Those same powers also understand legal attacks well; it is their field, after all. However, such tactics will not prove very succesful against Bitcoin, as there is no single institution to assault that can bring down the beast. Those attacks will bring down the unlucky retailers, but not the system; and attacking all such people becomes prohibitively expensive. The real attacks, when they do come, will be more direct upon the network in an attempt to undermine the faith in the network.