Jean-Paul sez, "Ryo and Yitz determine which day is the most popular day to go out to bars and pubs using the dates on photos from Flickr. Cool graphs included."
Exhibit B: # of pictures tagged "bar," by day of week
Sun: 2917 (21.0203934568%) [896]
Mon: 2803 (20.1988902501%) [795]
Tue: 2949 (21.2509908482%) [780]
Wed: 2690 (19.3845932118%) [840]
Thu: 4196 (30.237082943%) [941]
Fri: 5101 (36.7586654176%) [1185]
Sat: 5540 (39.9221733804%) [1301](Square brackets show number of unique users who posted images.)
(Thanks, Jean-Paul!)