I always sit on my own toilet, and on the toilets of close friends and family.
Not because someone told me to. I just prefer to sit when I wake up, still tired and dizzy. And if you had fun during the night then standing and aiming isn't exactly the best idea if you care about urine splashing all around the toilet.
And during the day I also sit by choice, it's just more relaxing. And who knows, maybe a number one will turn into a number two. Standing just doesn't make any sense to me, unless you really, really like the pissing minigame.
Now, the dick touching the porcelaine is indeed a problem on certain toilets:
http://becauseican.co.za/wp-content/...tch-Toilet.JPG
Thankfully I don't own one of those and neither my close friends. What a stupid design anyway, even if you sit to poop you will have your turd a few inches from your body. Dip into that!
You don't have any issues with this kind:
http://sharonwater.com/wp-content/up...ite-bkgrnd.jpg
unless you've got an errection (in which case you also wouldn't piss standing).
That said, I would never sit on public toilets and I certainly appreciate that I have it easy on festivals, concerts and the likes.