I like a girl who is confident and even rebellious in her sexuality. Somehow when a girl does something dirty (e.g., farting, pissing, spitting, etc) in public, it says something about her self-confidence. I like the "I don't care" and "I like to fart and I'll fart whenever I want" attitude.
This is why desperation videos do nothing for me. I would rather a girl crap her panties deliberately rather than by accident.