I don't work at Eastern but suspect the numbers are similar at most of the regionals...
My understanding is that a bond is pretty much un-enforcable from an industrial relations standpoint. I suspect that the whole requiring people to pay upfront is to slow the flow to better paid overseas positions, a bond will not achieve this. Contrary to popular belief, I don't think the airlines are worried about 'the money', but they are worried about losing staff in ever increasing numbers in the future...