Unlike the attorney-client privilege, the work product doctrine does not primarily rest on the confidentiality of communications between lawyers and clients. For this reason, work product can be shared more easily with third parties without causing a waiver.
In Sheets v. Insurance Co. of North America, No. 4:04CV00058, 2005 U.S. Dist. LEXIS 27060 (W.D. Va. Nov. 8, 2005), the court held that a personal injury plaintiff did not waive the work product protection by sharing work product with others involved in a boating accident. The court noted that those to whom the plaintiff disclosed the work product shared the plaintiff’s interest in obtaining insurance coverage for the boating accident.
No court seems to have articulated the difference between the commonality of interest required to avoid waiver of the work product doctrine and the “common interest” required to avoid waiver of the attorney-client privilege, but logically the former should be much broader than the latter – because the work product is not as fragile as the attorney-client privilege.