Hugo Schwyzer wrote an interesting piece on "Indexing Your Sex Life: Why and How We Keep Fuck Lists." He called on his social media connections to give stories about their lists. Some 78 women and 31 men replied.
Quick data from the drive-by "study": Women were more likely to record details beyond names and numbers, men were more likely to limit their lists to women with whom they'd had vaginal intercourse, and Schwyzer heard from people with lists as small as three and as many as 640.