Though Facebook's calling Mark Zuckerberg's Shanghai trip a "vacation," whatever the Facebook CEO is doing over there with his girlfriend Priscilla Chan doesn't look like too much fun. Zuckerberg and Chan were spotted touring the city together by Chinese bloggers on the popular microblog platform Weibo. As you can see from the photo above, Zuckerberg doesn't look too happy. But maybe that's all the stress from the possibly, very unsubstantiated rumor that the Facebook man has gone to China for business.

The official word is "vacation," but the sight of Zuckerberg has Chinese bloggers wondering if this visit might have deeper meaning. "Does this mean... Facebook is preparing to be unblocked?" said Kelisisong on Sina, a popular Chinese microblog service, via Channel News Asia. About 450,000 people access the social network illegally, according to The New York Times. But Facebook does not yet have a legitimate presence in China for reasons it blames on the Chinese government. "We continue to evaluate entering China," Facebook said in a filing with the SEC. “However, this market has substantial legal and regulatory complexities that have prevented our entry into China to date." But because of the country's ginormous population, Facebook COO Sheryl Sandberg has expressed interest in expansion over there, especially in light of all this we-need-to-prove-our-worth IPO stuff going on. "Given our track record so far, I have confidence that we have a good shot at winning whenever it makes sense for us to enter [China]. But we need to figure out what that is going to look like," she said in an interview with Bloomberg Businessweek.

Not one soul has spotted Zuckerberg meeting with any of the big Chinese Internet players -- something he did on his last China jaunt -- but the manager of PopCap, a mobile gaming company, claimed to have seen Zuckerberg alone on his lunch break.  "Priscilla Chan is not with him. So is Zuckerberg dealing some business over there?" asks MIC Gadget's Star Chang. Plus, Apple CEO Tim Cook is also over there. And although he is in Beijing and Zuckerberg in Shanghai, some have rumored the two shared a jet and are doing some sort of tech-giant business over there together. 

Even if Zuckerberg's on a regular vacation, from the sad, tired looks on his face (via Reuters) it doesn't look like he's enjoying himself. 

While there, we know for sure the couple has done some shopping at an Apple Store a vague "Chinese market" as well as Tianzfiang, a "famous renovated residential area," as Chang describes it. From his modest lifestyle, we know the billionaire CEO isn't much of a shopper. Perhaps the consumption, and not business dealings, has put that sour look on his face.