I would only like to add that RMgick for example provides free method to 
release large images if they are not needed, and for me that's good thinkg.

solution to the above problem might be finding a way to assign Qnil to 
all references before forcefully removing actuall value.

this way we would be able to release for example large file that we 
loaded into memory becouse we had to do bunch of regexpes on it.
Or if someone is making image manipulation library in pure ruby it would 
be nice to be able to free that 20mb large bmp :]

greets