Delta Airlines allows 1-2 hamsters in the passengar cabin. The cage counts as carry-on luggage and must meet with carry-on size limitations. Delta allows only 2 animals in the cabin at a time, so the airline must be notified at the time the tickets are purchased.

There are some conditions:

Fees: $45-$60 (independent of cabin or cargo). In cargo, the fee is per cage, and animal quantity is unlimited.
Age: Hamsters must be at least 8 wks old at the time of travel.
Health: Each hamster must have a veterinary statement of good health within 30 days of travel.

(Hamster Haven)

So - the hamster would earn miles?