I always uncheck mine as commercial as I am not trying to sell anything or send anyone to my site off of hubpages. I leave the ad level at high for most of my hubs. If the ads are too disruptive I will remove them. I still have ads and plenty of readers. There is no change in number of ads if it is marked commercial or not. When I first did it I suspected that my traffic went up, but that was a long time ago. I think that the commercial nature changes how search engines see you. Keep in mind, if you have a commercial site it does need to be checked as such.