Founded by former English teacher Jack Ma in 1999, Alibaba's goal is "to make it easy to do business anywhere". It does so by offering a platform where vendors can sell their wares, and currently controls about 80 per cent of China's e-commerce market through websites such as Tmall - where Apple, Nike and Gap have online storefronts - and Taobao, which is home to 8m sellers. Over 230m buyers used its retail websites last year, or close to 40 per cent of China's internet users. And almost $250bn-worth of goods were sold on them last year, a third more than Amazon and eBay's transaction volumes combined.
Alibaba makes money through commissions, selling prominent advertising space to sellers, and service fees. Those areas have proven lucrative - its sales rose 57 per cent to $6.5bn (£3.9bn) in the nine months to 31 December, while post-tax profit quadrupled to $2.9bn. And it already boasts big name investors such as Yahoo - which owns a 22.6 per cent stake - and SoftBank, the Japanese telecoms group, with a 34.4 per cent stake.
And it's not a one-trick pony, either. Alibaba has a small business loans division, a cloud computing business and an online ad exchange. And it has spent over $3bn on acquisitions in the past year, including a department store chain, China's largest video-hosting site, US car-hire start-up Lyft, a mapping service, a luxury e-commerce site and a shipping business. It seems to prefer partnering rather than buying foreign companies outright, which might draw the ire of Chinese politicians.
But some aspects of Alibaba may worry investors. It plans to give a team of 28 in-house executives the power to appoint the majority of its board. Alibaba freely admits that will limit shareholders' influence in corporate decisions, but claims it will enable it to focus on long-term profits. And it seems less than enthusiastic about life as a public company. In a letter to employees, Mr Ma likened the IPO to "a gas station along the road to the future", and has repeatedly said "customers first, employees second, shareholders third".
Another concern will be government intervention. Alibaba's size exposes it to anti-trust scrutiny, and it already has to monitor its websites for 'superstitious' and 'socially destabilising' content. Fully-audited accounts may prove a pipe dream, too, as US inspectors will need the Chinese government's blessing. Moreover, fake merchandise and copyright infringement are rife on its websites, which risks it being labelled a den of thieves.
But perhaps most unsettling is that foreign ownership of Chinese internet companies is restricted. Alibaba investors will own shares in an offshore vehicle called a "variable interest entity" (VIE) that simulates ownership of Alibaba's assets through contracts. That raises the prospect of Chinese legislators deeming the structure illegal, or Alibaba's owners seizing its assets by withdrawing them from the VIE, as they did with payment platform Alipay without informing Yahoo.
Regulation aside, as more and more people abandon desktop PCs for smartphones and tablets, another issue may be whether Alibaba can make money in a mobile world. It claims its focus is on adding mobile users and improving their experience rather than making money. But the limited advertising space on smartphone screens could spell trouble for the business.
True, Alibaba's mobile transaction volumes climbed to almost 20 per cent of its total volumes in its fourth quarter, from 7.4 per cent a year earlier, and over a quarter of China's 500m mobile internet users use its platform monthly. But as that growth tails off, shareholders will want to see mobile profits. Alibaba may look to emulate Facebook, which faced the same doubts, but now earns over half of its advertising revenues on mobile.
Alibaba has already taken steps to build its mobile offerings, buying stakes in mobile web browser UCWeb and TangoMe - which owns mobile communication app Tango - and increasing its stake in China's Twitter-like Weibo. That should help shore up its defences against rival Tencent, which owns two of China's most popular social media and messaging apps, QQ and WeChat. The latter directs its 355m active monthly users to JD.com, another e-commerce company readying itself for a US listing that could threaten Alibaba.
