The Association of Learned and Professional Society Publishers conducted a survey of academic book publishers policies and practices in online publishing in 2009. The initial results of that survey are available (released in Oct. 09) with additional results to follow. More information can be found on the ALPSP site.
From the ALPSP site: The First Findings Summary (pdf) published on 13 October 2009 draws attention to:
* the size and extent of the forthcoming survey;
* the types of academic publishing currently being undertaken;
* the reported effect on sales of the ‘Look Inside’ function provided by Amazon;
* the number of publishers so far signed up to the Google Book Settlement;
* the proportion of eBooks published by commercial as against non-profit publishers.