In his “Creative Commons Statistics from the CC-Monitor Project” iCommons Summit presentation, Giorgos Cheliotis of the School of Information Systems at Singapore Management University estimates that there must be more than 60,000,000 Creative Commons licenses in use.
Based on backlink search data from Google and Yahoo, he also provides the following license breakdown highlights:
* 70% of the licenses allow non-commercial use only (NC)
* Share-Alike (SA) also a very popular attribute, present in over 50% fCC-licensed items (though SA is anyhow self-propagating)
* 25% of the licenses include the ND [no derivative] restriction