That being said, it's always made me feel weird in a way I struggle to articulate. It seems cool to offer an opportunity to someone who needs it, and referral bonuses are nice for workers.
But it does seem to go against the spirit of referral bonuses.
I suppose if companies were really upset by people hacking their referral system they could simply fix their online application process so that it doesn't go nowhere.
Looked at a different way, the companies are essentially paying bonuses to their engineers to do resume screening. It seems like if that's what they really wanted they could ask people to do it as part of their job though.