Not really an option on most forum software (surprisingly.). Dunno about Fusetalk in specific.
In reality, making a minimum number of posts can hinder some possible deals and will encourage people to random spam threads just to get the minimum amount and possibly making newer members not hang around. IMHO, it's always been easier to PM a mod or make a post alerting other to the post being spam than it has to make other restrictions.
You'd be surprised at the lengths spammers will go to.
Hot deals gets a LOT of lurkers that often find some really good deals. (Like the free laptops I signed up for the other day!... KIDDING.) But seriously... it hurts just a slight bit more than it helps, I believe.