There are just some things you don't wear on a motorcycle...and a thong WHILE wearing a short skirt is mostly likely #1 on that list.
What was this girl thinking?! I can't imagine any reason (aside from being kidnapped while wearing a skirt and thong and being forced to get on the back of someone's motorcycle) for any woman or man for that matter to wear a thong that the wind can easily let everybody around you see. Including a passerby who just happened to have his cell phone at the ready to take a video of it. Watch it for yourself and prepare to laugh.