A few notes:

It is worth paying attention that at least the MT9D111 module I have has two power ground pins. While one is obviously (and right next to) VCC, the connection for the second ground pin is not entirely clear or explained in the EBay description of the pinout. Looking at the Micron datasheet itself, my guess this would be the 'analog ground', though those features don't appear to be pinned out here. In any case, I decided, at first, not to take any chances and spliced two wires into one coming off the pins into common ground just to be safe.

Also worth noting is that while many i2c devices utilize addresses in the 1-127 range (the typical range of most i2c scanners), this device utilizes a range at least up to 0xFF (255), so when testing for good comm (Ack/Nack) make sure to alter your scanner code accordingly.