Like many other folks in the points & miles world, I've been using a combination of Vanilla Reload cards and Amex's Bluebird card to "manufacture spending" in order to generate miles and meet initial spending requirements. If you don't already know, Vanilla Reload cards can be bought with credit cards at some locations, most notoriously at some drugstores. VRs can then be used to reload a variety of prepaid debit cards, such as the Bluebird. The Bluebird can then be used to pay off the credit card with which you purchased the VR.
VRs used to look like this:
Flytertalk thread, VRs have a significant security flaw. When you activate/load the card there is a ten-digit code on the back of the VR that you use to reload your prepaid card. On older VRs, that code is covered by a gray "scratch off" strip. However, as some have observed, the strip can easily be removed with a razor blade or other implement without leaving a mark. Here you can see that I've removed the strip and reattached it to a different location on the card. A criminal could just as easily remove the strip, write down the code, replace the strip, and leave it for an unsuspecting customer to purchase.
Fortunately, Vanilla has finally implemented a better security measure. The new cards look like this:
This was a much-needed improvement and should help thwart the type of fraud discussed above. Well done, Vanilla.