Usually the ban is the first warning. I sometimes PM users giving a friendly warning but can't do it for everyone as it's very time consuming and sometimes they don't listen anyway. Though it may seem harsh I think the best course it to learn from it and put more effort into making relevant posts on their return.
I am first time going to praise the MODs for this action as I used to always feel that the forum is not being moderated due to the amount of spam/scam taking place here.
It's a request to even check the Digital Goods section where people are openly selling fraudulent goods, Amazon accounts and even their bitcointalk account. It's illegal and such topics shouldn't be created. I have recently witnessed a case wherein a Hero Member with positive trust sold his account and the buyer was a fraud who went to scam another person who sold him a product just because of his stats.
Scams aren't moderated here and there is sometimes a legal grey area on certain things though we do usually remove stuff that are universally illegal (though you must remember sometimes something is legal in other places and not in others and sometimes something is not actually illegal just frowned upon and for othertimes it is hard to definitively tell (Starbucks cards may be obtained illegally but they also may not and we usually don't have proof either way). Also, what Hero member account are you talking about? It is quite rare that an account is bought to scam or at least that they're successful in it, but people should still use escrow and not just trust a random account because it has a little bit of trust.