The main problem with this is that some (many?) of us care about finding deals from more than one airport. Right now (ignoring how poor Ding! has been lately) I feel constrained by only being allowed to sign up for 10 cities. Now, if they allowed sign-ups for as many airports as desired, with deals delivered by e-mail - that would be the best of all worlds (again, assuming that the deals get back to their prior values).