I wonder, is there any way to estimate the % of brainwallets (either by number of accounts created or amount of funds deposited) that have been compromised? This would take more than just blockchain research but I'm curious as to whether researchers have taken a stab at understanding just how bad use of brainwallets really has been. 1%, 10%, 90% lost?
There's really no way to know how many SHA256 (or similar type) brainwallets exist, because the public information (the address, and possibly public key) looks just as random as something generated by a more traditional wallet client. It's not until you crack the passphrase that you know it's a SHA256 brainwallet.
As I've surmised previously in the thread, I suspect that a lot of thefts do not go reported, publicly anyway, because the typical person who uses a SHA256 brainwallet is probably not very technically minded, and may not think to find a forum such as BCT where they can ask for help. Pride may also play a part. I imagine there's a fair few exchange support tickets asking about a withdraw that "didn't work".
I think that showing how funds can be stolen within literally seconds is a pretty powerful indicator of the potential risk of using a SHA256 brainwallet ... but those same non technically minded people may never find that information.