In response to this column:
http://www.straightdope.com/classics/a2_330.html
Clocks/watches, when being photographed, are set to 10:10 in order to “frame” the watchmaker’s logo. The logo is always placed under the “12” on the clock/watch face. Any other postion of the hands would detract from the viewing experience of the all important consumer. And it would most likely irritate Messrs. Rolex, Omega, Movado, et al.
This may sound incredibly stupid, but really what isn’t concerning the world of marketing?
Anyway, it’s my understanding that clocks are set to 10:10 because it looks as if the clock is smiling, which makes the clock look friendlier, which makes more people want to buy it, which…well, you get the idea.
It sounds ridiculous, but I’ve heard it from a number of people from a number of different professions (professional photographers, marketing folks, etc…). So, if it’s a fallacy, at least, it’s a fairly wide spread fallacy.
Um, folks, ever hear of Occam’s Razor?
You see most clocks and watches at 10:10 because, duh, most photo shoots start at 9:00 am, and by the time the art director and client and account executive diddle and fiddle with things it’s about 10:00 before they start shooting ANYTHING, and after maybe 126 shots it’s about ten after ten, when finally the art director says, “okay, I think we have it”
I’ve been there. I know this.
That would be 10:10 PM? Correct.
Because there is no way in H*** that any gathering of ad agency and client personnel could come to a consensus in less than 1 hour. 
being in charge of many photo shoots, I’ve never even started the set-up for a shot before 10am… the first hour is spent unloading product, selecting a backdrop, and getting the photography gear set up… then there’s the lighting, which typically takes another hour or two… so a ‘9am photo shoot’ will generate the first frame around 11am at the very earliest
I have to admit that I’ve included clocks and watches in several setups, and I always take the batteries out and set the clocks for 10:10… why? because it’s sort of an inside joke among marketing people… do we think it will increase sales? no… but we do it so we can look at each others’ work and go "hey, I see you set the clock for ‘happy time’ "… seriously
That assumes that the watch in the shot is both functional and set to the correct time. It seems likely to me that the watch would not actually be running, especially if it has a second hand, as the photographer would not want one of the hands obscuring the manufacturer’s name, and it seems wildly, wildly unlikely that the watch, almost certainly manufactured in another state, if not another country, than the one in which it is being photogrpahed, would happen to be set to the current local time. Lastly, I find it flatly impossible to believe that any photo shoot would be ready to start shooting with barely over an hour of preparation.