5 million online DVD subscribers

This article["Video policy: Better late than never"] from the Boston Herald online, is about how the abolition of late fees at Blockbuster could cause them inventory problems. Not anything we didn't guess before, but for one little tidbit buried near the end: "according to Adams Media Research... nearly 5 million subscribed to a mail-order DVD service last year - such as Netflix, Blockbuster's own service or WalMart's". That's a figure I've never heard before. We know that Netflix claims only 2.5 million. Blockbuster has bragged they gained .5 million in six months. That's only 3 million. Does that mean Blockbuster has more, or is the remainder all Walmart's? Perhaps that figure is comprised of all online DVD renters combined. Quite a number.