Last week's four-hour breakdown of Sina's micro-blogging service, China's largest, sent ripples through the nation's Internet world and raised some interesting questions about its development.

At about 10:30am last Wednesday, users found they could not log onto the popular t.sina.com.cn, which boasts 50 million users. People often say, "if it ain't broke, don't fix it." It could be equally said that most people don't realize how important something is until it is broken.

Many Sina's micro-blogging users first suspected the blackout was caused by some glitch on their end. Frantic to get the connection back up and running, they busily refreshed web pages, turned mobile phones on and off, uninstalled and then reinstalled software. All to no avail.

The incident clearly highlighted not only the popularity of the service, but also how Chinese Internet users have become increasingly "addictive" to the practice of sharing up to 140 Chinese characters with their friends any time, anywhere and via any device. That's pretty much like Internet users across the world.

However, unlike other countries, where the microblog sphere mostly revolves around Twitter.com, it's still an open battlefield in China. Many websites are developing their own proprietary micro-blogging systems. The problem is: They don't connect with one another.

Micro-blogging services suddenly have mushroomed on websites of different media, cities and industries.

The micro-blogging competition among portal websites, such as Sina, Sohu and Tencent, has virtually started a war. They are furiously signing up celebrities for the official openings of micro-blogging accounts on their websites, hoping to lure users to their sites with big-name endorsements.

Such competition is moving China's Internet services into an environment of "Chinese walls." Fanfou.com, China's earliest major micro-blogging website, last week quietly resumed its service on an invitation-only basis. However, users found out that one of its key features - connecting updates on Fanfou with instant messaging services such as MSN and QQ - is now defunct. Neither can new Fanfou users search contacts or invite friends to this platform by importing their contacts from MSN or QQ.

Blocking the import of contacts from instant messaging services could effectively throw a big monkey wrench into the development of micro-blogging service providers because people who gradually build lists of their social relations on instant-messaging platforms want to use them on micro-blogging sites.

The situation is unlikely to change. QQ doesn't want to share with a micro-blogging competitor the social contacts its users have built up on its platform. On November 11, Sina signed a cooperative deal with Microsoft to bundle the MSN service with its blog and micro-blogging platforms.

So it was no surprise Sina's micro-blogging updates won't show up at QQ messengers and vice versa.

It's understandable for firms to want to maximize their profits. But since the Internet has increasingly become an indispensable tool for people's daily communications, these attempts to red-line basic services violate users' rights to choose.

The likes of Sina and QQ should not be allowed to hijack users' contacts built on their platforms and hold them hostage against competitive services.

Quality, functions and openness of its platforms should decide the winner of the microblog battle.