So yeah, I was wrong. It turns out it was a gimmick after all. In addition to the stealth "Black" cards in Wal-Mart Blasters, there will also be a stealth "Throwback" version of 2009 Topps that's exclusive to Target Blasters. The plan was to release both versions in April, but Wal-Mart jumped the gun and released them a month early.
The Cardboard Junkie has, as usual, expressed the opinions of many Hobbyists. Most of what I wanted to write, he already covered, so I won't pile on.
I will leave you with this. If Topps, Wal-Mart, and Target got together to create a special-run exclusively for their stores, I wouldn't have a problem with it. The problem was the bait-and-switch.
If a collector purchases a Blaster of 2009 Topps Baseball, he/she has the expectation of receiving 2009 Topps Baseball and not a stealth parallel set that he/she was not aware of -- and probably doesn't want anyway. It really is like buying a can of tomato sauce and getting diced tomatoes instead.
And another thing. Is it really too difficult for the card companies, big box retailers, and distributors to, you know, actually tell us what's in the product before we buy it? Or am I asking too much?