this is probably a re-post but I just stumbled upon it today and found it very interesting.
summary: In advertising for wristwatches, most models are frozen with their hands smiling at 10 and 2 to frame the brand name and logo.
http://www.nytimes.com/2008/11/28/business/media/28adco.html?_r=3
I'm with you there, Nic.
I always thought is was down to symmetry and the fact that (in general) it keeps the hands away from the usual placement of day/date windows. eg. Quarter to 3 is a no-no. So go with 10:10 which is smiley, and after a while, it becomes almost a standard