I was once told that defying the almost ubiquitous alphebetisingalphabetising convention may create difficulties in referencing the paper later on. It is thus in all the authors´ best interests to stick to this convention.
IncidentlyIncidentally a similar discussion was recently had on the secret blogging seminarSecret Blogging Seminar:
http://sbseminar.wordpress.com/2010/02/21/et-al-is-unethical/“Et al” is unethical
(the discussion began on slightly different matters, but by around comment 20 discussion turns to precisely this question).