For as long as you only want to play with closest close-up photos, it might be an ok thing to do (I have always only done it by HOLDING the reversed lens to the camera, I've never even considered attaching it to it in any manner, mind you), but if you want to truly delve into macro photography, you'll very soon (within taking the first couple of pics!) notice all the limitations this method gives you.
But for a few first tests (and the surprise at how close you can get in that way!) it is yay. Anything further? Nay.