I've been exchanging some e-mail with a reader who thinks we're crazy for devoting so much space to Second Life. He's not the only one -- many critics think the media in general devotes too much space to Second Life. You don't have to look very far to find that attitude.

The objections aren't unreasonable. Second Life's user base is pretty small. Only 444,669 "residents" -- or separate accounts -- were logged on to in the past seven days, as of the last report, March 28.

And yet the media is right to devote significant attention to Second Life. I know I plan to continue doing it indefinitely, or until the bosses force me to stop.

Why? Because Second Life offers a glimpse of what the Internet will probably look like in 15 years.

The 3-D Internet is here to stay. I am dead certain of that, as sure as I am that the sun will rise tomorrow. Three dimensions makes sense for data modeling. It makes sense for diagramming; IBM showed me an interesting demo a couple of months ago of a business process rendered in 3-D in Second Life. And it also makes sense for some kinds of online shopping. For example, if you're buying clothes or furniture online, it's nice to be able to see the things at all different angles.

Right now, expensive, specialized tools do all those things. Second Life is nowhere near as good as those tools, but it's cheaper, and becoming more commonplace. That's how the Internet itself won out over more robust wide area networking technologies; Internet technologies were cheap and good enough.

Will there be practical, daily use for 3-D interfaces? I'm sure of it, even though I don't entirely know what they are, and even though I also know that many things will continue to be done in 2-D.

I also think -- but I'm not sure -- that the whole metaverse model used by Second Life and other online games will prove to be a powerful model for the 3-D Internet.

We have billions of years of evolution that designed our brains to be expert in dealing with the physical, three-dimensional world.

Moreover, we have thousands of years of preparation in imagining we're in another world. We do it every time we take in a story, whether that story is delivered in the form of a play, novel, TV show, or movie.

Second Life engages the same parts of the brain that we use when we watch a TV show or a movie and identify with the main character. When I see the avatar Ziggy Figaro on my computer screen, it's not just a cartoon character or a collection of pixels -- that's me in there.

But will Second Life dominate the Internet in coming years? Much as I love SL, I'm not sure.

To be sure, the market is its to lose. SL is growing fast. Users were logged in for 12 million hours in February, up 10% over the previous month and a fivefold year-over-year increase. Much of that user base is fiercely loyal. It's lined up major business partners including IBM, Cisco, Sears, American Apparel, Toyota, Circuit City, and Adidas. The technology is highly advanced.

True, World of Warcraft's user base dwarf's Second Life's. But WoW is a specialized tool, designed for one thing and one thing only -- playing WoW. SL is a general-purpose toolkit for building whatever you want in a a virtual world, which makes it the closest thing available to the future of the Internet.

And yet Second Life and parent company Linden Lab have significant problems. The platform is buggy. It crashes a lot, and it's hard to learn. The place is infested with pranksters -- known as griefers. And the sex and other adult content is insufficiently segregated, for many people's tastes, from the general-purpose fare.

I hear frequent complaints about Linden Lab being unresponsive to customer concerns. That's partially unfair; what users take for negligence is, in fact, an explicit hands-off strategy, designed to allow the community to evolve by itself, solve its own problems, and grow in a nonauthoritarian, pro-free-market fashion. All of which sounds great, but disgruntled users interpret that behavior as indicative that Linden Lab is a bunch of slackers who don't care about customers.

And, worst of all, you don't really own what you create in Second Life. Linden says you own the intellectual property to your creations, but it also reserves the right to kick you offline for any reason or no reason at all, so you'll never be able to access those creations again. It's no good to own something if you can't actually get to it. That's a big disincentive to people spending a great deal of effort and time building and coding in SL.

Linden Lab may well become the Google of the second decade of the 21st century -- dominating and defining the Internet, with gigantic revenue and profits and billionaire founders. But Linden Lab has a great many problems to solve first, and if it doesn't solve those problems, it will be flicked aside like a bug by a better competitor.

What do you think? Will 3-D interfaces become standard? Will the future look like Second Life? Will it be Second Life?