I suspect it's happening either at the store, or in the local distribution to the store. Twice now, I've had US Bank Mastercard GC's drained the day after I bought them. I bought the GC's at two different grocery stores (different location and chain, purchased 6 months apart) and in both cases, the cards (four total) were drained at a Walmart about 30 miles from where I bought them.

The first time it happened, I dealt with the Loss Prevention Dept of the store I purchased at, and they said they'd had a number of people report the same thing - and the cards were all being drained at this same Walmart 30 miles away. So clearly it's someone who has physical access to the cards.

ETA - in this most recent occurrence, one of the cards had a $0.01 charge at barnesandnoble.com the same night that I bought the cards, so I assume they're frequently testing their list of hacked cards, waiting for one to activate. They were in Walmart at 9am the next day to drain the cards.

Lessons learned - don't by US Bank GC's, and load and drain on the same day.