I was a heavy user of Upper Deck Kids in 2008 or 2009 window. You went online, entered the code, and received points for it that could then be redeemed for prizes. I think I finally saved up enough one time and ordered a hobby box of Upper Deck First Edition baseball. Most base cards were worth 5-15 points or so, but occasionally a nice rookie or insert would net you close to 100. I want to say my box cost me about 30,000(ish) - including shipping.
Once you entered a code, the card was in your virtual collection. You could also virtually trade, although trading for a card didn't get you any points for it. Small correction Spaz - either every copy of the card had the same code, or you couldn't use the same card for points twice. I want to say that all copies of a card had the same code. If a card was already in your collection, the code would reject.
The whole program was designed to get kids back in the hobby. I think it was supposed to be for kids up to 15. Then Topps tried something similar with ToppsTown, but those codes were only on inserts and their website wasn't as user-friendly. Then out of nowhere Upper Deck switched from putting codes on the back of each card to putting a single code inside wrappers - suddenly, for me, the cost wasn't worth it. I didn't buy much new; there was actually a pretty great community on UDK that utilized the forums a lot, just like here. Each sport had its own sub forum, which also had more sub forums for each team. You could go to any team forum and there would be plenty of threads with people posting codes from their cards for all to use. Between that and COMC, I'm sure that has quite a bit to do with why it stopped - you could get codes anywhere without buying any product. There was a daily point limit that I hit once or twice but it was still easy enough to rack up 100k points in a few days if you were so inclined.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.