I was curious about how many tags people put on their photos in Flickr and whether more tags help you get into interestingness. So using their fabulous api I wrote a quick program to count the number of tags for photos in interestingness and compare them to photos in the huge FlickrCentral group. Numbers are averages and standard deviations for both the author's own tags and for tags volunteered by others.
Author tags Viewer tags FlickrCentral 7.5 (9.1) 0.1 (0.4) Interesting 8.0 (6.4) 0.7 (2.2)
What's it all mean? Not much. The average FlickrCentral photo has 7.5 tags and the average Interesting photo has 8.0 tags. Well within the standard deviations, not a good predictor. Photos in Interestingness do have measurably more viewer contributed tags but that's not a surprise; photos in Interestingness have more viewers.
So not an interesting result, but I love how easy it is to do this kind of data mining with Flickr.
(For the record, I compared the top 100 interesting photos for each day so far in July, 1900 photos, with the 500 most recent photos in FlickrCentral).