While both companies saw explosive growth from when they were founded (both in 1962) until just a few months ago, when the retail sector imploded, the way in which they expanded was markedly different.
Whereas Wal-Mart spread from a central point like your traditional virus, Target was more like a metastasizing cancer, beginning in the central U.S., like Wal-Mart, and then popping up in targets of opportunity wherever there was good business.
And now, just like Wal-Mart, they to have a Gizmodo writer comparing their stores to something terrible that can invade the human body. Victory! [FlowingData]