This finding from Thomson’s Science Watch is fascinating:
The numbers of scientific papers published with more than 50, 100, 200 and 500 authors plateaued from 2000 to 2003, then experienced a sharp increase in 2005. That year, each group reached its all-time highest levels. More than 750 papers with 50 or more authors were published in 2005, compared with a little more than 500 the previous year. Papers with more than 100 authors grew by more than 50 percent from 200 from just over 300 in 2003 to an impressive 475 in 2005. Interestingly, papers with 500 or more authors increased from 40 in 2003 to 131 in 2005. This group saw the largest jump of all — a 200 percent increase. [Emphasis mine]
Papers with 500 or more authors? Those aren’t authors; that’s a researcher’s entire Facebook friends list.