Using a brainwallet has one advantage and quite a few disadvantages. The upside is how there is no software to trust when it comes to generating mnemonic recovery seeds for addresses. Users do so from memory, by using long strings or sentences that are not overly complicated to remember. This is also the fatal weakness of brainwallets, as humans tend to get sloppy when it comes to passwords, passphrases, and security.
Thankfully, the number of Bitcoin brainwallets is relatively small compared to the overall numbers. But that is not keeping researchers from trying to crack these wallets. Brainflayer is a tool often used for this type of purpose, and the tool has undergone several upgrades so far. With a 215% speed increase over the past year, the tool is hammering away at testing private keys.
http://www.livebitcoinnews.com/glimpse-world-cracking-bitcoin-brainwallets/
