A recent Reuters article quoted some interesting data about consumer spending on PC gaming. The item that investors might find compelling is just how much of that spending was attributable to online subscriptions.

The NPD Group, a marketing research firm, reported that Americans spent $1.4 billion on PC gaming in 2005. If you put that in the perspective of software sold for consoles such as Sony's (NYSE:SNE) PS2 and Microsoft's (NASDAQ:MSFT) Xbox platform, you'll see that the figure isn't necessarily too impressive -- after all, titles linked to portable systems such as the PSP and Nintendo's handheld units moved $1.4 billion in 2005 all by themselves.

But the big number here is $344 million. That's how much of the $1.4 billion went toward subscription-based services. That's a quarter of every dollar. And it shows a significant shift in the way consumers are willing to access leisure software.

Of that $344 million, a small percentage went to gaming domains -- only 15%, or a little more than $50 million. Cited in the article was Electronic Arts' (NASDAQ:ERTS) Pogo.com, a place where people who aren't necessarily into massively multiplayer online role-playing games, otherwise known as MMORPGs, can go to get a quick fix. The overwhelming bulk of the online sales, however, went to popular titles for hardcore gamers.

I think the percentage of subscription-based gaming to overall PC-gaming sales is exciting. I believe it shows that online gaming is going to be a huge growth phenomenon going forward -- and not just for the PC arena. All of the major console companies will be integrating online distribution as serious selling points for their wares, too.

Take Nintendo's upcoming Virtual Console initiative. That technology will allow Internet-connected consumers to download old games by Nintendo, Sega Genesis, and TurboGrafx. Xbox Live, meanwhile, has been very successful at signing up more than 3 million members, and Bill Gates believes that the Xbox Live network could have more than twice as many members as it does now in less than a year. Although Disney (NYSE:DIS) isn't in the console business, it, too, has recognized the potential of the online market for games by hooking up with Shanda Interactive (NASDAQ:SNDA) this week to bring digital Disney characters into Chinese territory.

None of this is to say that boxed software is going away. Nevertheless, if companies like Electronic Arts and Microsoft can continue to catalyze a migration to the online-subscription model, then not only can margins and cost structures improve, but also the ability to target advertising to gamers will most likely become a value-adding revenue stream, considering that online technologies should make such initiatives quite simple and efficient.

That might end up being the bigger element of this story -- can software companies really make a go at selling advertising? I think they can. In fact, they must. I read an interesting statistic concerning development costs for the new consoles -- for truly cool games, a $20 million budget won't be atypical. That increases the stakes. Anything that can help amortize some of those costs -- yep, advertising is what I'm thinking of -- will be helpful.

This NPD data shows that online gaming is here to stay. Investors in video-gaming stocks can be confident that a lot of long-term value will ultimately arise from subscription fees and advertising revenues.

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Shanda is a Motley Fool Rule Breakers recommendation. Electronic Arts is a Motley Fool Stock Advisor pick, and Microsoft is a recommendation of Motley Fool Inside Value . Take your favorite investing service for a free, 30-day trial.

Fool contributor Steven Mallas owns shares of Disney. The Motley Fool has a disclosure policy.