Based on the thread subject spelling, I bet I know what inspired this post...

See the
heroin store thread for a discussion along similar lines.
My own opinion is that the US government loves to point to a technology, and make arguments in court along the lines of "the majority of uses are illegal / infringing / evil / etc., therefore, any use of that technology strongly implies illegality" I'm not making a political statement about drugs or gambling; that's just the practical reality one finds with today's law enforcement.
The best way to make bitcoins a success is to convince legitimate, tax-paying, paperwork-filing merchants to accept bitcoins, and customers to pay them in bitcoins. Similar to how bitcoin's network remains intact: as long as >50% of the network is not evil, we need >50% of well known merchants to be upstanding citizens in their respective jurisdictions.
One day, inevitably, law enforcement will have a bitcoin-related case, and having evidence of bitcoin's beneficial nature will be powerful and useful. Concrete example: presenting bitcoin as a way for donors to charities to remain anonymous is a powerful, positive argument for bitcoin.
If the bitcoin "brand" is generally considered to be a den of thieves, scam artists, tax evaders, and criminals, it gains increased law enforcement attention, and will be marginalized away from the general public. I want bitcoin to be as broadly successful as possible.