I've sold them all to Reese. If I did hoard them to sell here, I'd be the lame person that keeps 1-3 in stock, so if I ran out, I'd be out until I found it again.
I did for a while, but then I got tired of storing them in my museum's second floor so I just stopped buying fortune cookies altogether. Most of the time I'd get repeats of the same item anyway. I didn't find them interesting to begin with, but I do have a soft spot for the Wii Balance Board (only item I actually have a liking for).
I collected most of the items and than quit. Sold all but the Hero clothing and the other clothing set.
Later I added another town and had to use up the fortune cookies for my catalog.