Are Celebrity Accounts on Private Social Media an Oxymoron? Ask Chinese Pop Star Wang Leehom.

The value of a celebrity user on a social media service is often more than an endorsement. It’s not just “drink Gatorade because I say so” — but rather “follow me, and I’ll let you into my life.” But that doesn’t exactly work on a private social network, where the whole point is intimacy and reciprocity.

For instance, despite her recent endorsement of Path, Britney Spears — someone who almost everyone knows a little and very few people know well — is not necessarily a natural fit for the personal network. In order to keep within Path’s limit of 150 friends, Spears’s team is reportedly planning to rotate fans through the available slots.

Another way private social tools might handle this weirdness is to effectively “break” themselves for celebrities — to let super users have super powers to communicate with lots of people.

This week, the private mobile social network Weixin did exactly that, with one of the biggest celebrities in China, pop artist Wang Leehom. For background, the American-born singer has released 25 albums since 1995, with an eclectic musical style that’s heavy on romantic ballads (see below). He’s a spokesman for Coke, Nikon, Nike and others.

Meanwhile, Weixin is a mobile messaging app from Tencent that has seen explosive growth in the past year, with more than 100 million users. Users can send voice, text, pictures and video updates in one-on-one or group conversations. Almost everything is private; users are limited to 20 friends, and there are no public posts.

Wang Leehom is one of the most popular users of Sina Weibo, with 16 million followers, and he just performed the first solo pop concert at the Beijing Olympics venue the Bird’s Nest on Saturday — for an audience of 90,000.

On the occasion of the concert, Tencent expanded Weixin to allow Wang to connect to his millions of fans in a more personal way. Through a custom integration, Wang Leehom’s voice, video and text updates arrive in users’ inboxes, in line with their private conversations.

That way, when users send replies to Wang within the app, they go directly to him. Tencent had to design a Web interface for the product so Wang Leehom could deal with the volume.

There’s actually a Silicon Valley angle here — the whole arrangement was brokered by Andreessen Horowitz partner Connie Chan, who is a personal friend of Wang Leehom’s. For now, it’s exclusively available to him.

This isn’t a totally new idea; I’ve written a bit about a “voice Twitter” with celebrity users called Bubbly that’s big in India and elsewhere, and is backed by Sequoia Capital. But it’s particularly interesting in the recent context of the rise of mobile social apps and more private alternatives to Facebook.

On April 12, the day his celebrity Weixin account launched, Wang Leehom sent out a short video message that almost immediately brought down the Weixin servers, and he received 220,000 replies from fans, Chan told me.

When I spoke to him earlier this week, he said he’d gotten about 600,000 video responses alone, including people singing to him, reviewing Saturday’s concert and telling him not to stay up too late.

“It feels like I’m sending them a text message,” Wang Leehom said of his Weixin account. “It’s very familiar. I think people almost feel like it’s more personal to receive a message on a cellphone than to see someone in person.”

A careful and conscious social media user, despite his many brand endorsements, he writes his posts himself, and will rarely, if ever, include sponsored content or personal promotions. He said he tweets from his Sina Weibo account once a day — at night — so his fans know what to expect. A typical post gets tens of thousands of comments.

But Wang Leehom is not cross-posting his Sina Weibo updates on Weixin. “Because the medium is different, you can share different things,” he said.

For example, he said, the day he performs at a concert, he makes a practice of not talking at all, in order to save his voice. His team and his friends know well that his lips are sealed. So, this past Friday, before the Bird’s Nest show, he recorded a Weixin message, saying, “This is the very last thing I’m going to say today.” Fans loved that intimacy.

I doubt that the combination of a celebrity presence and a more private social network will always make sense. As soon as more celebrities come on board, this will become less of a novelty — and these networks won’t really be private at all. But maybe it’s less about the network itself and more about the intimacy of mobile.