Like the title says, I'm conducting an informal survey of Bitcoin's biggest challenges. Specifically, I'd like to hear what you all think are the biggest challenges in three categories:

• Technically - As in the Bitcoin client, the operation of the system, mining, security, etc.
• Culturally - As in mainstream acceptance, user and merchant adoption, Bitcoin's image (or image problem), etc.
• Practicality - As in the practical uses and difficulties in Bitcoin (a good example would be people who worry over wait times for confirmations).

There's no need to limit your answers to one per category; feel free to pose as many as you like for each category or post answers to just one or two of them. Your answers can be as detailed or straightforward as you please.

Thanks, and I look forward to reading your responses!