I belive that the limiting factor applies to Netscape Browsers, however consider, if any domain could set any number of cookies imagine how much cookie information you could accumulate on your hard drive. All sorts of maniacs could store piles of wasteful information on your disk.
Cookies should only be used to store at max a handful of values for session awareness and the odd piece of personalistion data. If you need any more than this stored get a backend data-base.