Well of course there are exceptions. Personally I've tried the "emailing from my laptop while riding a bicycle" thing - you take your hands off the handlebars, swing your backpack around (that's the hardest part and most likely to bring you of-balance), take out your laptop, open it, wait for it to come out of sleep and compose and email with one hand while holding it with the other. Of course on an empty park path with a friend to watch out for other people. Depending on the inherent stability of the given bike frame, and the weight of the laptop, it's actually not that hard...