Basically, users are not quite fond of protecting their accounts by not using a security question, that, is the very best assurance of security you can have in forum. And most of the hacked accounts as you can see are those accounts for sell, without having escrow, if i am not mistaken.
The reasons why people are getting hacked are most likely not only because of the security question feature. There are a lot of ways of people getting hacked. I personally think the #1 reason is still that people use the same passwords on multiple accounts; and if one of those account's password gets leaked, then the hacker pretty much has access to almost every account the user has. And that's just the tip of the iceberg. There are lots more ways.