OK, time for a reality check.  (You may be depressed by the following.)

The most popular app of the bunch, TripAdvisor’s Local Picks, has fewer than 2,000 “active” users = daily users, more or less.  Per Adonomics, it’s the 859th-ranked application on Facebook right now, lagging behind things like Vibrating Hamster at #673.

Like many Facebook apps, Local Picks rose fast and fell fast.  At one point in December 2007, it clocked more than 100,000 active users, but it’s fallen below 10,000 for most of 2008 — below 5,000 for the past two months.

More worrisome is the fact that, despite its collapse, Local Picks still has more daily users than the other 13 apps on my list combined.  Almost twice as many, in fact.

The second most popular app on my list is Restaurants by Hungry Machine with more than 500 daily users, down from a peak of more than 10,000.

And that application, in turn, has as many users as the remaining 12 apps combined.

In short, local-search usage on Facebook is loooooow right now.  And it’s heavily concentrated in a couple of apps, both of which have cratered in 2008. Based on Adonomics charts, I suspect that only a few other apps have any life in them:

•  DoYa? may be building a bit, perhaps based on its gift-cert giveaway

•  My Restaurants looks to have a small core of regular users that isn’t shrinking

•  iEat seems to be growing somewhat

But obviously, the numbers here are fairly inconsequential.  DoYa? is the biggest of the three, with 215 active users.

So — yikes, right?

Yes and no.

On the one hand, it’s easy to see how Jon Carder of MojoPages concluded that local search isn’t worth doing on Facebook.  (See earlier post.)  On the other hand, I think we can learn some things that’ll help us crack the code:

•  Recognize the potential. Local Picks is a good app, and it grew nicely in November and December to top 100,000 active users. That’s a number worth noting. OK, in December it suddenly crashed. Maybe someone can tell me why?

•  Leverage success. The two biggest apps have more popular “sibling” products on Facebook; none of the others do. Hungry Machine explicitly presents its apps as part of a family, using a toolbar to link between them. TripAdvisor doesn’t do this, but it does some lesser cross-promotion from Cities I’ve Visited. Most of us can’t draft off an earlier app, but there are other ways to apply the lesson.

•  Attract repeat users. Most local apps either never took off, or peaked and then fell off a cliff. But several — Eating and Hangouts, for instance — took off and then went into a slow fade. While a fade isn’t as good as a rise, it’s better than falling off a cliff: These apps didn’t lose people immediately. Interestingly, they share a focus on broadcasting “status”-type messages, which may be a key to keeping users engaged.

•  Keep working the problem. It’s striking how many Facebook apps are abandoned, more or less, once they start losing users. The charts tell the story: No secondary upward blips as new solutions are tried. The users are allowed to melt away. This isn’t limited to local, of course. Building a Facebook app is an experiment rather than a strategy for many developers, and it shows. But given the potential of local — and its importance to some of these players — I’d expect a bit more dedication to figuring out what works.

That’s the end of this little series of posts. Soon I’ll tackle the question of how Loladex can avoid the fate of its Facebook competitors.