All of the HP laptops that we get at work come with those modules to slide into the empty bays.
The IBM laptops come with the "blank" modules already installed, and I have to remove those and insert the CD-RW drive.
Never saw the option for those when I bought my Dell, though it probably would be nice to have one for weight reasons
I normally run everything on my laptop through my desktop anyways.
I'm not gonna pay $10 for one though