The Facebook verification sidebar misses the point; attempting to play ball in the China payment transactions market would be a herculean task for any foreign company or investor group.

First of all, it's a scale business, and Alipay's 1.3 billion users plus 80 million merchants is nothing to sneeze at.

Second, even if you had a business plan that could get you close to those numbers, you'd need to carefully navigate China's tightly regulated legal landscape in one its most sacred sectors (financial services / banking). Back during my PE days, few firms were brazen enough to seriously attempt such, and most of those that did (e.g. HSBC, BofA, Citi, Standard Chartered, Google) failed to come remotely close to achieving their objectives.

Third, assuming you were to find a willing Chinese bank to partner with, and established a JV in which you invested up to the legal limit (49% iirc), then you'd need to acquire users/merchants and get tight with thousands of regulators throughout the country that your competitors have already enriched.

Fourth, no matter how good your relationship with your JV partner is and how advantageous the agreement is, you still don't control the combined entity, and if management changes, you could end up completely screwed.

Fifth, country/political risk is substantial (i.e. the banking sector could collapse, the laws could be revised to your detriment, zhongnanhai could simply decide that it doesn't like you, etc).

Most of these hurdles aren't really China specific (e.g. you'll encounter similar even in small markets with more inviting bureaucracies like Singapore), but few would dispute the notion that China's landscape is much more formidable than average.

As a corollary to this, it's worth highlighting that neither Baba nor Tencent have made concerted efforts to penetrate markets other than mainland China (they barely have their toes wet in HK, Thailand, Taiwan, etc) in spite of the fact that both have considerable expertise and can't really grow much bigger at home.

In short, Twitter could theoretically try, but I don't think it is nearly brazen enough to do so, and if it did, I'd rate its odds of success at less than a tenth of a percent. Do I need to remind you guys what became of Uber in China (note that, unlike banking, ride-sharing was a nascent industry 10 years ago, so they had the luxury of helping to define the rules)?