My addiction really came home to me when I went to France, where you can't get the stuff (or I couldn't find it anyway) and I experienced quite powerful cravings. Something like I imagine smokers feel on quitting, only without the concern for one's health.
The only other time I have had food cravings was when I was pregnant. At that time I craved calcium. I started by chewing chalk and limestone, but when I figured it out I started buying health food tablets of Dolomite (a kind of digestible limestone) and crushed oyster shell. You have to be careful because normal calcium supplements have Vitamin D in them, which is dangerous in excess, so I had to avoid those due to the amount of calcium I was wolfing down at the time (like two week's supply in an afternoon).
Like calcium, flaxseed is quite bland and crunchy/chewy. I have never met anyone else who actively likes the stuff. But I find the sensual process of eating it much more satisfying that (say) chocolate.