Hi,
Last summer I posted here to say some girls on my team were having doubts about bunhuggers, which are mandatory for all female athletes at my school.
Since then I've trained and competed in outdoor track, volleyball and XC and always have worn the black Nike spankies that the school provides.
Now I would have to say I'm so used to them that if someone asked me to wear shorts for a sporting activity I'd feel really weird in them. It'd be like I had something to hide.
IMHO bunhuggers because are better for competitive sport (less wind resistance, no chafing, encourage you to keep in shape and promote a professional image for the team). I think schools and coaches that mandate them are right to do so because if they were optional, probably hardly anyone would wear them because they wouldn't want to feel exposed or have others think they were showing off.