Here is the criteria we use:
Ratio of Loved It to Not For Me
Ratio of # comments to time in member review
Diversity of commenters
Quality and length of comments
Feedback from the SG Photographers
Model activity on the site (blogs, comments, groups, etc.)
We don’t just pick the sets with the highest number of comments, although often the sets with the highest number of comments are chosen because a high comment count often goes hand in hand with doing well in other criteria. Any set in member review is eligible to be the Set of the Day, just because your set does not go up on the front page right away does not mean that you should lose all hope, we have been known to buy sets that have been in member review for several months to a year.
The number of sets a girl has in Member Review can sometimes affect whether or not we buy a set. If a girl has multiple sets in Member Review, we will not always pick the set that has the most comments - we’ll choose the set that we think is the best reflection of the girl.
So, basically, the fewer sets you buy, the better, because it’s all free content that you make money off of while the model and photographer get nothing.