Brain wallets are unsafe. This is either a mistake, either a bad choice of words.
The seed for HD wallets (which some may confused with brain wallets, until they learn) is, on the other hand, secure if created with a proper good tool and in a safe environment, but should not be memorized as a backup. That's a sure way to lose the funds! The seed has to be kept safely, offline, in a written form. People forget, people suffer accidents or strokes, human mind is just not good enough.
And two more tips:
* consider buying hardware wallets for your coins if you plan to spend
* always double check the addresses you paste and the amounts you send when you do transactions.
I guess by Brain wallet, I mean the seed for the SHA250 encryption that produces the Private Key. Can be any combination of letters, numbers, words, etc.
But imo, Hardware wallets have been shown to be unsafe, hacked, privacy issues and hardware malfunctions. Can you recommend any good ones?