From View From the Wing:
Offer is valid until August 1, 2008 for rentals of one day or longer at participating airport locations in the United States and Canada. The bonus can be earned up to 3 times. And don’t add any other AWD number (Avis) or BCD number (budget) to the reservation.
That’s an incredible offer! I’m very tempted to start collecting some DL miles with all of the bonus offers they’ve had recently. While their FF program leaves much to be desired, it’s hard to turn down when they give away miles for basically nothing.