Why? I also have one of these optibay's, and it doesn't contain any active parts: It's just a piece of metal to make your drive fit in the place of the CD drive. Why does this cause issues on the SSD's?
The same reason why putting SSDs in external enclosures is extremely inconsistent - power. An SSD needs significantly more power at certain times, depending on the controller. Most of the time, an optical bay does not provide the necessary amperage.
I think your facts are a bit off. The "superdrive" in macbooks require significantly more power than a SSD. When you burn a dvd using the superdrive, it requires between 40-50W of power. Even the most power hungry SSDs during heavy sequential write mode use less than 5W of power. If anything, the optical drive bay needs to provide more power than the HDD side of things.
It's more likely that the ebay-knockoff adapters were poorly made than it having anything to do with power requirements.
Oh, that is exactly what I meant - the Optical drive bays are all made very badly, and intended for HDDs. The motherboard/connection can certainly power any drive fine, but the replacement bay cannot.