Scalability and decentralization. Basically, the thing that makes bitcoin bitcoin is what makes it weak. Decentralization is cool on paper, but every revolutionary project needs guidance and one genius man behind it (Steve Jobs anyone?) The second thing is scalability. In order for bitcoin to be mass adopted, it needs to become scalable AF. However, this are not failures that will bury bitcoin. I'm a true believer and I see a very bright future for btc.