Rockstar Games released its highly anticipated add-on to "Grand Theft Auto IV" this week. "The Lost and Damned" is out exclusively for Xbox 360 (sorry PS3 fans), and can only be purchased by download through the Xbox Live Marketplace for 1600 points (that's $19.99 in real-world money). Also of note: You must have a copy of "GTA IV" to get this to work.

I've yet to download the add-on (in my case "The Lost" is the dollars allotted for fun money in my checking out thanks to the “Damned” economy), so we won’t get into a blow-by-blow review of the game. Here’s a short version: Instead of being Niko Bellic, the eastern European immigrant, you’re now Johnny Klebitz, longtime member of a longtime biker gang known as the Lost. You have lots of new weapons and vehicles at your disposal to bring more terror on Liberty City, all while you listen to a bunch of new songs on the game’s soundtrack.

But while you’re admiring your handiwork with sawed-off shotguns and Molotov cocktails, you can bet the folks at Rockstar (and just about every other company in the video game industry) will be studying the success of “The Lost and Damned” very closely. Here’s why:

- Weren’t we just here? “The Lost and Damned” has been released to the public just 10 months after “GTA IV” hit store shelves and began its warpath to the top of the sales charts. For the hardcore GTA fans who have torn through every mission, stolen every car Brucie Kibbutz has wanted and shot every pigeon in Liberty City, an add-on couldn’t come fast enough. But when you’ve got one of the top-selling games of the year, odds are you’re catering to a lot more casual fans, many of whom still haven’t gotten all the way through the original game. How thirsty are these folks going to be for more “GTA”? And to think: This add-on was originally projected to hit the virtual shelves back in the fall.

- Where are we going? Here’s where it gets really interesting for the gaming industry. Xbox Live has been successful offering simple new games, old favorites and small add-ons for regular releases. This is a departure from that formula. Sure it’s an add-on for a regular release, but this isn’t a three-song track pack for “Guitar Hero.” This is a robust release being billed as “a new episode” of “Grand Theft Auto IV.” Just remember when we get to the point where we’re downloading full games, this is the bridge that was built to get us there.

Which leads us to …

- No vacancy. The Xbox 360 I got a little more than a year ago has a 20 GB hard drive, and it’s a pretty popular model. You don’t need to be a math major to figure out that you’re not going to fit many full games on a 20 GB hard drive. But fear not, Microsoft is all set to sell you a bigger hard drive to hold more games. So for every however-many games you download, you’re going to eventually need more storage space. And then you can buy another hard drive. Cha-ching! See where this is going?

But a lack of storage space for you means …

- PLENTY of vacancy elsewhere. While you’re filling up your hard drive with more games, guess what you are NOT doing? Trading them in to local stores for credit toward your next purchase. Rockstar has released “GTA” spin-offs for older consoles. You can walk into a used-game store and buy games like “Vice City Stories” for cheap now. But since “Lost and Damned” is a download, you won’t be seeing any low-price used copies on store shelves or eBay. And sure, maybe Xbox eventually drops the download price on “Lost and Damned” after a year or so. But that isn’t going to put any money into local stores that generate revenue through used-game sales. In “GTA” terms, it’s not exactly a sniper shot from a rooftop to the resale industry, but it’s most definitely a whack in the knee with a pipe. And if one day we get to the point where people download all their games through services like Xbox Live instead of buying discs from local stores? Well, let’s just say there are a lot of local merchants and national chains that would rather you didn’t just read that last sentence.

OK, I’m not trying to come across as some conspiracy theorist wing nut here. One downloadable add-on for one game on one console isn’t going to throw the entire video game industry into chaos. But make no mistake: Video game makers are watching this experiment very closely.

So get out there and shoot some bad guys. Rockstar is counting on you.

- Tom Valentino