Mohamed El-Erian writes:  The Alibaba IPO will be a very big deal, with potentially marketwide impact. At a possible $22 billion to $24 billion, it could well be the largest IPO in history. So it really matters how investors fund their purchase of Alibaba shares.

The broader market would be least affected if the incremental funds came from a healthy and sustainable increase in borrowing, associated with a greater willingness (and ability) on the part of investors to assume risk. The deployment of idle cash would also have minimal effect on the rest of the market. Although both will occur to some extent, they are unlikely to be the main drivers.

This leaves plenty of potential for downward market pressure as investors sell existing holdings in order to make room for their Alibaba purchases. Given that most investors don’t know as yet how many shares they will receive, most of the selling wouldn’t materialize until quite far into the IPO process. The combined effect could be quite significant.