Well, no, and the more familiar observer will say, "Of course not! You knew it was in alpha/beta all this time!" That is true, of course - if you've seen a single Minecraft video or screenshot, you probably noticed the Minecraft Alpha v.xxx or Minecraft Beta v.xxx up in the corner of the screen. I would say that this distinction is largely academic - yes, technically the game may fit under either of these headers (and of course there is flexibility to define things like the type of beta - open or closed - etc.), but given the developer's own approach towards updating the game:
"It’s a bit tricky to really do a release for Minecraft as we keep updating it all the time. For one, the version we deem as the “full version” won’t be very different at all from what the game was like a week ago, and we’ll keep adding features after the release as well..."
- It's hard to really say that there's ever going to be some traditional end to the alpha/beta stages with all their hallmarks (code freeze, final RC, etc.). That is all to say that the game could probably be viewed as simply released when it became open to public use - after all, shortly afterwards, users were able to pay to play it (in alpha, no less). The concept of continual support after release - or at least bugfixes - also falls squarely into the model of game release used by many (if not all) major publishers as well.
So why is there a release date at all? I think it's a pretty savvy move to use these traditional appellations (alpha, beta, RC) in the realm of a game that clearly falls outside their conventions. Like many single-user-developed (or small-team-developed) hobby/indie games, what we really see here is an author who's invested a lot into a product and wants to keep developing it, even after he's done. Is that sustainable? Smart? I don't know - Minecraft's dev(s) seem to be doing at least all right for themselves. However, I'd bet that there's a reason why many large companies have one release date - one big "holiday" for themselves - instead of the protracted release cycle used here.
And that's why I think it's a smart move to use things like this - this otherwise-meaningless release date. It's an easy way to drive attention to your game - and it's clear that is the goal (using a memorable number (11-11-11), tying it in with other big releases (Skyrim)) - and perpetual attention can really only be a good thing for a game's sales. I think if Notch (Minecraft developer Markus Persson) is smart, he'll keep using this strategy. Instead of making updates simply patches with numbers attached, he'll release them in the style of titled, downloadable content, even if they're no different than patches - because at the end of the day, the attention is what matters.
(Minecraft "release" announcement: http://notch.tumblr.com/post/4423138657/11-11-11)