Names were done in foil only, no printing beneath it. So, if a sheet missed the foil stamping machine, "NNOF" (no name on front). In this case, as already stated, it's simply a printing flaw, and not an error (where in the case of the 1990 Topps Frank Thomas where Topps went back and had to change the way the cards were printed and is therefore classified as an error). You may find a player or team collector who wants the card and it might fetch a small premium. But you'll probably not see life-changing money for it. :)
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).