I think the biggest problem with bitcoin is that most people don't understand it.

I'm a programmer and a nerd and I don't fully understand it. This is a problem that assumes bitcoin should be a widely adopted currency, used by the mainstream (as I do). This problem is large, but solving it is easy. Most people only need to know how to use it. All currencies are complicated, like dollars, but once you use them a few times it feels like second nature. People will be a bit awkward using bitcoin at first, but they will get the hang of it. Most people don't know how U.S. dollars work either, they just know they can spend them, how to spend them, and if they are lucky, how to make them.

Another big problem is that governments can't control bitcoin like fiat currency. They can't print it up to go fight wars whenever they want (could be a good argument for bitcoin bringing peace). This is a problem because it's made bitcoin even more volatile, made bitcoin out to be a house of cards that the government flick over with one finger. The government is the elephant in the room full of bitcoin.

(It's a good thing there aren't a lot of Americans who know what went down with Chinese QQ coins, because I think they would have even less confidence.)

The infrastructure is super weak, at least for now. People aren't going to give a shit about bitcoin until they can buy their Starbucks with it. With a whole community full of hackers, there doesn't seem to be very many solutions. We should build something like Square (product) that accepts bitcoin credit cards. Or, better yet, skip credit cards altogether and process bitcoin payments from smart phone to smart phone.

I'm not super worried about the weak infrastructure because I can see how much capital is being dumped into building the infrastructure. For example, Coinbase and Bitstamp seemed to spring up overnight. After using Coinbase to buy, sell, and transfer coins, you'd be pretty stupid to ever want to use Wells Fargo or Bank of America's shitty systems. For now, I'm just waiting for the storm of bitcoin infrastructure solutions to hit the market... it's going to be crazy.