Are all blog readers FTers? Are they all 'gamers'? I think not. It could be that a significant proportion of blog readers use the referral links but don't game the system significantly.
Card issuers either know blog readers are a risk, or they know blog readers, by and large, turn into the type of customers they want. Or it could be that card issues just don't care what blog readers do. They may trust their own systems to weed out gamers.
Either way, the bloggers don't deserve venom. Not much is changing here. If you were gaming, you will keep gaming.