Blackberries are a weed in Illinois, too, but the ones growing wild don't produce very nice fruit, which is I guess what makes them profitable to grow. A transplanted wild plant, when cared for properly, will make a much larger berry. The wild ones are tiny and mostly seed.
http://en.wikipedia.org/wiki/Luther_Burbank
The modesty with which he wore his scientific fame repeatedly reminded me of the trees that bend low with the burden of ripening fruits; it is the barren tree that lifts its head high in an empty boast.