Users must register with their real identities will probably delay the company’s revenue-generating plan until the second half of this year.

"That will create a lot of negative sentiment with investors," says Alicia Yap, an analyst at Barclays Capital. "The post-New Year rally will not be sustainable."

Such concerns were reinforced this week, when government officials said that Weibo users who failed to register under their real names by March 16 would no longer be allowed to post messages. Local media have reported that only 3m new users have registered on Sina Weibo over the past month  down from about 20m in earlier months.

The company’s share price already reflects some of these concerns. Following a series of government moves towards tighter censorship of social media, and falling profitability because of the soaring cost of marketing Weibo, Sina shares have lost 54 per cent since their peak of $142.83 on April 19 last year.

Sina has not been idle, though. "The company has been working hard to lay the ground for monetization, and it is moving closer," says Dong Xu, a social media expert at Analysys International, an internet research company in Beijing. That includes hiring engineers to strengthen its skills in developing applications and to adjust its platform to new needs.

Unlike Tencent, China’s largest internet company by revenues and Sina’s main rival in the social space, Sina is essentially a media company. Advertising accounted for 77 per cent of its 2011 revenues of $484m, Morgan Stanley estimates.

Investors hope the company can build a business beyond advertising, similar to Facebook, which last week filed for its long-awaited stock market debut to raise $5bn. Such a model would resemble Tencent, whose broad spread of revenue streams has made it much less vulnerable to cyclical swings when advertising falls.

Sina has taken steps to prepare for that, including the launch of a gaming platform and a virtual currency. But that is all at an experimental stage and there is skepticism about some areas of monetization.

"So far, most things are free," says Xu Zhiming, founder of Kuaishubao, an online bookstore that uses Sina Weibo for its order management and customer relations.

Sina has made its gaming platform free of charge for the first year. Even if it were to start charging, analysts’ expectations are very low. This is partly because Sina’s user base, which consists largely of white-collar workers in China’s largest cities, "are not gamers", says Mr Dong of Analysys.

That would leave Sina with advertising. The two main areas of potential here would be the country’s soaring e-commerce market and highly targeted ads similar to those on Facebook. Many Chinese e-commerce sites have already linked up to Weibo, but Sina has yet to demand a revenue share for that.

The biggest disappointment for industry experts has been lack of progress in targeted ads.

"In theory, Sina has an incredible asset with all this user data, but they don’t appear to know how to analyze those data," says a Beijing advertising agent.

Despite healthy advertising demand in general, that weakness in reading the data impedes progress, especially in the current political climate. "Brands worry that they could be tied to re-tweeted messages that might be sensitive," says Barcap’s Ms Yap.

All these things are much less of a problem for Tencent. Although it has a microblog of its own, the Shenzhen-based company sees the service mostly as a tool to wear down Sina and make sure it does not challenge Tencent’s lead in social networking in China.

Says a Tencent executive: "We have no plans to monetise our microblog. We don’t need to."

Foreigners are to be offered free treatment for HIV on the NHS for the first time under controversial plans backed by ministers.

Those from abroad, including failed asylum seekers, students and tourists are currently barred from receiving free HIV treatment  unlike other infectious diseases.

However, the Government is to support proposals recommended by peers which will end the "anomaly" and allow free treatment even for those not legally settled in Britain.

Campaigners argue that the free treatment is essential as it reduces the risk of Britons being infected  and can help people to be treated for HIV before their condition becomes serious and life-threatening.

However, ministers are braced for criticism that the decision may prompt so-called "health tourism" and put the NHS under financial pressure at a time when hospitals are being forced to find cuts. It typically costs up to ￡7,000 a year to treat someone diagnosed with HIV and an average of ￡300,000 per patient over their lifetime with the disease.

Last night, Anne Milton, the public health minister, said: "This measure will protect the public and brings HIV treatment in to line with all other infectious diseases. Treating people with HIV means they are very unlikely to pass the infection on to others."

However she added: "Tough guidance will ensure this measure is not abused."

The Government is understood to have decided to introduce free treatment amid fears that the potential costs of being diagnosed were dissuading foreigners from seeking help. There are estimated to be 25,000 people, many of whom are foreign-born, undiagnosed HIV sufferers in Britain.

The Health Protection Agency recently calculated that it costs more than ￡300,000 to treat every person who contracts the disease including those who go on to develop AIDS. The cost of treating sufferers in the last stages of their lives is particularly high.

The government believes that early diagnosis of sufferers could ultimately help cut costs before the virus is passed on to other people.

If diagnosed early, HIV, although incurable, is now treatable for many people. According to the National Aids Trust, many people taking anti-HIV drugs become non-infectious.