For my selfishness, bitcoin already is a success. I've already received a good ROI, so even if bitcoin goes to 0 in a month I'll be way better than before, anything more is a success for me.
But I personally doubt bitcoin will fail in the long run. Maybe replaced by something better. Bitcoin is p2p, so not easily banned, and the blockchain tech is really a innovation.
There have been so many things that when they appered no one would say that they would go much far away, and they ended up conquering the world. Why not bitcoin? I think its good stay anyway, if it fails(not to happen soon) you can get good ROI, if it success you might be the next Bill Gates.
Bad rep in the media....child porn....gambling...drugs....51%.........blah, blah...
What's wrong with gambling and porn? They have been here way before bitcoin, and I think that 99% of people from gambling and porn industry don't even know what bitcoin is. Also the closest porn thin I've seen in the bitcoin world are cam girls that accept bitcoin.
drugs: the drug money is mostly cash and fiat. Addicted people have thei brain too damaged to learn something relatively complex like bitcoin, and the druglords sometimes are poor people without access to education and computer. For me the cash money is way more drug-related than bitcoin, even in the best case scenario of adoption. About 50% of money paper has traces of cocaine, when they arrested that big Mexican cartel guy they found a billion in cash, not in bitcoins, at least 25% of Wall Street money has relation with drug money laundering, and so on.
51% attack: would be too expensive, and with limited concrete effect, except the big crash in price that would happen. Also anyone with so much hash power would be making a huge profit, so it would be like burn a stack of $100 and all your future incomes, like Joker did in Batman the Dark Knight. I think no one rational enough to get at that point would be stupid to do such thing. Even if he's against bitcoin, there are more discrete and effective ways to hurt it in the long run while taking profit.
Plus the CS already made miracles with software and algorithms, so it is possible that when bitcoin skyrockets, or after a 51% attack, these issues would disappear.
CP: when they say about that, they think more about deep web and tor, not about bitcoin.