Aug 27, 2012 · 3 minutes

In the US, location-based flirting via mobile is a phenomenon that is only beginning to take off, and the field is becoming cluttered as hopeful startups crowd into the space seeking domination.

In China, meanwhile, an app called Momo is showing to the world the potential of mobile for facilitating casual hook-ups and insta-dates. Since its launch a year ago, the app has accrued 10 million users. This week it received a massive $40 million Series B round, according to various reports (the Global Times put the figure at $50 million), with Alibaba rumored to be among the investors.

According to a statement on its Sina Weibo account, Momo – which has an English tag line of "Hi, stranger" – boasts 2.2 million daily active users and processes 40 million messages a day. The app is now growing at 1 million users a month.

Part of Momo's success in China can perhaps be explained by the dynamics of the dating scene, which are skewed by demographics in which males vastly outnumber females. Many people are shy about making connections, or have trouble finding suitable partners through traditional channels. For that reason, online dating sites such as Baihe and Jiayuan have proven immensely popular, but their focus has mainly been on matchmaking – in other words, helping people find partners for life, which in Chinese culture is a pressing concern.

Momo, on the other hand, is adept at helping people find partners for the night, or just a few weeks, even though its founders have claimed that it is already responsible for many weddings. And it's not just popular among locals.

While I was in China recently, several expat guys showed me the app and hailed its utility as a tool for hooking up with attractive Chinese girls. It may be that there's some appeal in the idea of having an app that connects people who aren't looking for "serious" relationships, too. Expats and overseas-born Chinese I talked to in China made frequent mention of how quickly their local partners would become deadly serious about their relationships. Often, the word "marriage" is mentioned within the first few weeks of dating.

Trust and security issues may deter some people from using services such as Momo, whose Chinese competitors include Mojing and Youjia, as well as the more general purpose messaging app Weixin (WeChat). As I reported last month, Baihe now requires users to sign up with verified identification, which ensures that members know what they're getting and reduces the likelihood of scams. And there have been some negative news stories related to location-based dating apps in China. In June, for instance, a 32-year-old man was sentenced to eight years in jail for raping seven women he had contacted via Weixin. Prostitutes have also been found to use Weixin to solicit business.

However, Momo's million-users-a-month growth rate suggests that such scares are not enough to hold back the power of this emerging platform. In what is probably an unintended use case, taxi drivers are even turning to Momo to book new business by responding to demand from users nearby – a kind of ad hoc Uber. But let's be honest, sex is the seller here

In the West, startups such as BlendrSkout, MeetMoi, SinglesAroundMe, Assisted Serendipity, and LikeBright are trying to jump into the causal dating space, which Grindr famously – and, in terms of the sex aspect, more blatantly – staked out for gay hook-ups. Perhaps the most likely to succeed, however, is the UK's Badoo, an online dating site that is ramping up its mobile presence and launched in the US in March. In April, the company announced it had poached veteran Googler Benjamin Ling as its chief operating officer.

Badoo claims more than 150 million users, which makes Momo seem like a baby. For now.  As its huge B round attests, this baby is just getting started.