At TechCrunch Disrupt this week, Mark Zuckerberg enthused about Facebook’s money-making potential for mobile, but how exactly the company will start realizing that remains a mystery.

I’ve argued this before, but we might find that Facebook takes its cue from Tencent’s Weixin, China’s leading mobile messaging app. Weixin has many of the features that Facebook has – profiles, timelines, photo-sharing, a social graph – but it was built purely for mobile.

How has that worked out for them?

Well, Tencent founder Pony Ma has just told an Internet conference in China that by the end of this month Weixin will hit 200 million users. That’s a fifth of Facebook’s total, except it’s just one market. More impressive: Weixin has been around for just 19 months. It took Facebook five years to get to 200 million users.

Weixin is an emerging social network masquerading as a messenger. In fact, it is pretty much an inverse Facebook – a messaging app built for mobile that leverages the address book and ties into other social networks in order to grow its social graph.

Meanwhile, Facebook had the graph in place first and now appears to be trying to turn itself into a messaging product for mobile. One very obvious difference is that Weixin (available in English as WeChat) offers voice-messaging and video calls, which is great for those of us who hate to type text messages on pokey smartphone keyboards. Could Facebook follow suit? Given its partnership with Skype, I’d say it’s inevitable.

If Facebook does start offering audio messaging and video calls through its mobile messaging app, then the broad-strokes line between it and Weixin becomes almost indistinguishable – except that rather than provide all these experiences in a unified experience, Facebook would be splitting them between apps. I’d bet that doesn’t last for long though.

Weixin already has strong monetization potential. Nike and Starbucks have run campaigns on the app, and Tencent has opened the platform for third-party developers to build other apps on top of. It will also have a game center through which Tencent will no doubt push many of its enormously popular and profitable titles. This is, after all, a company that built up a $60 billion market cap through in-game purchases.

Other reasons that Facebook might be looking to Weixin for cues were outlined in very clear terms in Ma’s speech to the conference. In September, China’s mobile Internet users will surpass 400 million, he said. More than half the messages sent on QQ – Tencent’s dominant instant messaging service – are sent through mobile, while 53 percent of the 200 million pictures uploaded to Tencent’s social network, Qzone, are taken with phones. China, in other words, is experiencing the same trends to mobile that we’re seeing in the US – just on a larger scale.

That means it is a useful barometer for what might and might not work well in mobile in the West. As Ma explained, the easy-to-install/easy-to-delete nature of apps and the virality of apps distributed through the app stores can make or break a product in a brutally short period of time.

“I’ve found that the critical period for an app is less than a month,” Ma said, according to a translation provided by TechNode. “Usually a successful app will become very popular in three to seven days after its release. If your product hasn’t made a mark after a month, you have to think about innovating and change.”

The intensity of that process proves that Weixin is a durable and useful product. Facebook, no doubt, will be studying it carefully.

By the way, if you want to give WeChat a whirl but don’t have any friends to play with, I encourage you to download the app and add me as a contact. I’ve been using it with a handful of friends, but I’d be willing to take on a few more. The UI sucks, but the overall architecture and technology is pretty interesting. My WeChat ID is a40246421. No penis pics, please.