Not so long ago, calling something “Web 2.0″ increased its value. It meant fresh, new, interactive, responsive. Now, if someone uses that term you know they’re woefully out of touch.

For me, it’s been a trip to re-adopt my former web beat on GigaOM after spending a few years writing for our sister site NewTeeVee. I made the leap to the world of web video in the fall of 2006, when YouTube had just been bought, Facebook had just opened to the general public, and only a few people cared about a little service called Twittr.

Since then, one thing that’s gone by the wayside is the term “Web 2.0,” which got its start as a marketing phrase to build a conference around, and spawned both a new class of companies and sites dedicated to writing about them, such as TechCrunch and Mashable. TechCrunch, whose original tagline was “tracking Web 2.0,” itself declared the death of the term in February 2009, citing a perceived drop in the number of pitches mentioning it. Indeed, while the AJAX-y web services and user-generated content at the core of Web 2.0 haven’t gone anywhere, now the preferred term seems to be “social media.” Google Trends says that search volume for “social media” surpassed “Web 2.0″ right in the middle of January this year, though the new hotness has yet to reach the heights of “Web 2.0″ circa 2007.

Feel free to chalk it up to a matter of trendy semantics, but here are the material differences I see between these two mini-eras:

Building for the Mainstream

These days, starry-eyed entrepreneurs are building for the mainstream, not just for themselves. One of the reasons I was happy to leave the GigaOM Web 2.0 beat the first time around was that I didn’t want to write about yet another social bookmarking service trying to copy the innovative but narrowly used Delicious (then spelled del.icio.us, which kind of says it all). Sure, one of the best ways to come up with something truly useful is to build something you yourself want, like a repository for saving all the web sites you visit — and as Twitter has proven, niche products can evolve to satisfy the needs of those beyond just early adopters. But some of the most exciting new services online today are aimed at serving broader interests, such as the search for deals (Groupon, Gilt Groupe), and procuring real physical products and human services (Alice.com, Sears’ ServiceLive).

I think MySpace and Facebook deserve a lot of credit for bringing the Web 2.0 era to the mainstream, helped along by major portal offerings like Gmail. Those services and products continue to provide value to a broad audience. On the flip side, startups like Foursquare and the many folks who pitch us on, say, tweaks to Google Reader aren’t building with Middle America in mind. They may get there eventually, but not just yet.

All the World’s a Platform

The rise of platforms, app stores and mobile makes web applications better, more accessible and more useful. Facebook, with its platform launch in 2007, showed the value (and eventually, the dangers) of building on top of someone else’s pre-existing audience, making use of inherent viral channels and the continuity of experience provided by a popular platform. The distribution power of the platform was huge.

Then the iPhone App Store came along, offering far more functionality and exposure to developers (if they could get through its approval process). On the user side, just about every web app is better when it rides along in your pocket, ready when you need it. The iPhone and all the knock-offs and competitive one-ups it has inspired are tremendously popular. And as a corollary, the benefits of the mobile app platform model is now so obvious that the number of them grew to 38 from eight in the span of 2009 alone, according to new research.

The Most Obvious Answer

Of course, the one thing that affected every business, web or otherwise, was the economic downturn. However, Web 2.0 startups — until of course their funding ran out and/or they had to layoff employees — seemed woefully out of touch with the rest of the world.

Valleywag, which never missed a chance to declare something dead, might have actually been right when in it ran with the headline “It’s the end of Web 2.0 as we know it” in reference to a carefree music video released by Web 2.0 entrepreneurs cavorting in Cyprus to the tune of Journey. It was October 2009. Their timing was pretty bad.

Meanwhile, one of the sectors hit hardest by the downturn was the media, which was already being brought to its knees by its failure to adapt to the web. Now, your Facebook newsfeed really is your hometown paper (though its investigative reporting skills may be limited to relationship status changes), and Twitter really is your personal real-time newswire. And accordingly, social media referrals from sites like Digg and Twitter are increasingly important to media business models — and sites like Facebook and YouTube are among the most-trafficked, and therefore most powerful, on the web.

Maybe “social media” just sounds less like a buzzword or a brand name than “Web 2.0,” while at the same time pointing to a sort of social facelift for all content — a feature that can be included or integrated into everything on the web, rather than being segmented in its own category. Or perhaps it was the futile attempts to brand disparate things “Web 3.0” that made people realize how silly the naming convention was. But “social media” has its issues, too. As Aliza argued earlier this month on WebWorkerDaily, many new web tools are just useful, not necessarily social. Perhaps what was wrong with “Web 2.0″ was that the term implied a fixed version — while it’s cute, the metaphor of a software upgrade doesn’t carry over very well in reference to something that changes every day. Innovation on the web is fluid and builds on itself, and that naming convention just got stale.

Middle photo and post thumbnail courtesy of Flickr user chegs.

Please see the disclosure about Facebook in my bio.