The Distilled Spirits Council of the U.S. reports that using sex to sell alcohol, and depictions of excessive or irresponsible consumption - are the two main causes of complaints.
Two ads were mentioned as examples:
SKYY Vodka (print) which featured - shock, horror - a female model wearing see-through clothing!
Svedka vodka (print) which depicted gratuitous nudity and degrading images of women.
Makes a change to degrading images of Iraqi prisoners.