Old topic, but I'll add this anyway...
Sadly it seems that no one has picked up on the fact that the OP is dd to copy data OFF of a 16GB device. Therefore it is moving all 16GB even the unused space. This is very different from using dd to put an raspbian image ONTO a 16GB image.
Consider doing this on a device that has identical read and write characteristics (which none do, but...):
- use dd to place 2013-02-09-wheezy-raspbian.img onto a 16GB device
- use raspi-config to resizefs to fill the disk
- use dd to make a backup of the device
In this simple senario you copy
Step 1 moves 1.8GB of data and takes about 20 minutes
Step 3 moves 16GB of data and takes about 180 minutes
This happens even though there is only 1.3GB of data on the device (as reported by du -sch).
The tool dd is not ideal for this. I suggest using bzipped tar. Full SD recovery becomes a little more complicated because you will want to reimage the device from the original image and the use tar to replace the contents on the data partition. However, it is very simple to extract a subset of files from a tar. So, it's a tradeoff.