From a purely moral standpoint, I think refusing to pay inactive addresses is wrong. It's due payment for past work, it shouldn't be pushed back indefinitely. It also punishes the creation of new addresses, which beats one of the selling points of mining here ("virgin coins"). There is already a "new address tax", there shouldn't be any more.
New address tax?
Yeah well, nothing significant, but whenever you create a new account you increase the cumulative rounding down. It's just a little, but it's something (you are on average (~0.67
BTC/2) * number_of_addresses overdue).