When it comes to useless inventions, I'd add the "Spring Tension Shower Curtain Rods" near the top of the list. Yea, they dont have to be cut and will fit any "normal sized" shower area, but I have to wonder how many people have gotten bruised heads from those damn things falling.
Our house had one of them, and it had a lightweight plastic shower curtain on it. More than once I've opened the curtain and that rod slipped down the wall, so that I'd have to readjust it. Last night I dropped a bath towel in the tub. I wrung it out by hand and tossed it over that shower rod to dry. This morning, the towel, curtain, and rod were all laying on the bathroom floor. Apparently a wet towel is too heavy for that worthless piece of crap.
Tomorrow I'm buying a REAL shower rod that screws to the wall, or just some screw on rod holders and a piece of 3/4" EMT conduit.