By 'largish' are you referring to their numbers or body size? I've never had it but I heard that meatloaf is very fattening.
I never knew about this balloon chasing thing but I guess you'd have to be in a small community for people to notice it. I understand that the chasers are drawn to the free food but even if they go as a one-off, would they still be paying for drinks or expected to buy a product on offer?
Although it's kinda tacky I suppose the chaser is really not doing anything wrong as the food and event have been budgeted for to promote whatever. I don't see any real harm unless one can show that balloon chasers are bad for business by precluding genuine customers.