When ReadyBoost presents itself via AutoPlay, which is what has happened in your case - it presents you with a message asking you if you want to use the device to speed up Windows - then it is meant to inform you if there is insufficient space on the media. There should have been a message prompting you to free space on device.
Normally, ReadyBoost should not autocratically delete user files on a device without user intervention, as the ReadyBoost option will present itself with AutoPlay every time the device is connected to the PC.
So in answer to your question, Microsoft haven't developed a harmful feature, but in your case something has unfortunately gone wrong and the feature has acted in a way that it is not meant to. ReadyBoost is actually a very useful feature, especially for PCs with a limited amount of RAM. It works best with a USB flash drive that you have permanently plugged into the machine though. It would only have been of benefit to you if never intended to unplug your camera from your PC ever again...