A comprehensive survey of the legal hold practices of 235 companies (90% from the United States) was conducted in the Fall of 2007, by www.ITPolicyCompliance.com. The report contains detailed factual information about the size of the companies, annual revenue and legal hold practices. A number of conclusions are drawn from the data collected and published in a comprehensive report titled: "Improving Results for Legal Custody of Information" (August 2008).
A press release for the report stated "[t]he research shows that firms with the lowest spending on legal settlements, legal fees and expenses in IT related to legal requests for information are all implementing the same practices, especially when compared with the practices implemented by all other firms." You can see the press release and download the report here: http://tiny.cc/Vgzmm.