Candid snapshots are often the best pictures because they capture the exact moment in which they were taken.  No other type of photo can possibly show the true nature of the subject matter.  This is one reason why Denver photo booths are becoming so popular today.  At many different events, you may see a photo booth set up and ready to take candid shots of all the guests at a single party.  The photos produced by the machine often show the way the guest actually is without being posed.  I have been to several parties where photo booths were free to use and this was one of the best party activities I had ever seen.