re: "I've seen reports of retailers starting to track customers with higher than usual return numbers."
I return a fair amount of stuff to HD (and Lowes) sometimes with a reciept, sometimes without. I'll buy extra fittings for plumbing or electrical work or extra wood just so I don't have to go back in the middle of a job. Been doing that for as long as I can remember. I recently bought $250 worth of wood, had someone help me load it into my trailer and then an hour later had someone one help me unload it so I could return it!
I've only been flagged on a return once and it was because I returned a bunch of plumbing fittings at one HD and then a couple of hours later found a few more in the van and stopped at a different HD. When I tried to return them, they had to get a manager's approval. When I asked why, they asked me if I had just returned a bunch of stuff at the other HD. I said yes but later found a few more that I didn't need. The manager said "Fine" and processed the return. Bottom line is that they are certainly doing some type of tracking.
My pet peeve is the fact that they always give me cash for returns when I made the purchase with a debit card. I don't see why they can't credit the debit card like just about every other store does. A couple of dollars here and there is no big deal, but I didn't need $250 burning a hole in my pocket when I returned the wood mentioned earlier.