I was once told that defying the almost ubiquitous alphabetising convention may create difficulties in referencing the paper later on. It is thus in all the authors´ best interests to stick to this convention.

Incidentally a similar discussion was recently had on the Secret Blogging Seminar:

[“Et al” is unethical](https://sbseminar.wordpress.com/2010/02/21/et-al-is-unethical/)

(the discussion began on slightly different matters, but by around comment 20 discussion turns to precisely this question).