The concept isn't new. Some people have been cutting out micro-sd card adapters and jerry-rigging flush mounts.
Today, I got myself a poor man's version of the nifty mini drive. It is simply called the MiniDrive. They can be found on Amazon. The Nifty minidrive comes in assorted colors and indentation for a paper clip to eject the adapter. Mine is a cheap piece of plastic with another cheap piece of tape that allows you to pull and eject the adapter.
Compared to a normal micro-sdhc sdcard adapter.
As you can see, a regular sdcard sticks way out of the chassis on a Macbook.
With this minidrive adapter, I now have an extra 64GB of storage. In fact, you can use the sdcard as a boot partition. Apple hardware boots off SD media without fuss. I now have Ubuntu 12.10 boots off microsd on a Macbook!