Has anyone's friends ever had I problem with doing this? I'd never dream of it, just curious, since I've heard a mixed bag of answers.
Never had a problem, if customs intercepts the package, which 99% of the time they don't, all they do is sent you a letter.
like lune said, 99% of the time it's not a problem. just find a reputable seed bank (dr. chronic, nirvana, etc) and you'll be growing good shit in no time.