yer you could imagine people would just flood the suggestions forums with everything, just so that they could chance the possibility of getting free supporter.
Its a nice idea though, some kind of reward mechanism for suggesting things that get implemented.
Maybe not lifetime supporter though - 3 month's free supporter I think for a suggestion which the BB's deem to be appropriately deserving. Maybe 12 months if its a really good suggestion.
At least that way, that person will still have an incentive to keep suggesting things :)