Keep in mind that if you give someone an invite and they abuse it (under undefined terms), they lose their account, as do you and everyone else you gave an invite to. We take a risk when we hand them out, so why should it be free? You can buy an FH code right now on SR for about $20. I've seen them go for as high as $50, so there's no reason to hand them out for free. And if people have to pay for them, they are less likely to abuse them.