Proportionality. The polestar of cooperation must be an understanding and agreement that the discovery sought and provided by both sides will be proportional. There is extensive legal authority for the proportionality doctrine that has been long embodied in Rule 26(b)(2)(C), including the mentioned Kleen Products opinion. Also See Seventh Circuit Principles Relating to the Discovery of Electronically Stored Information, Principle 1.03 (Discovery Proportionality) (The proportionality standard set forth in Fed. R. Civ. P. 26(b)(2)(C) should be applied in each case when formulating a discovery plan); Losey, R., Good, Better, Best: a Tale of Three Proportionality Cases, part one and part two (2012); Losey, R., Bottom Line Driven Proportional Review (2012); Losey, R., An Old Case With a New Opinion Demonstrating Perfect Proportionality (2011); Losey, R., Second Edition of The Sedona Principles and the Need for Proportionality (2007).

Also see Default Standard for Discovery, Including Discovery of Electronically Stored Information, Delaware District Court Committee  (2011) Standard 1.b.:

Proportionality. Parties are expected to use reasonable, good faith and proportional efforts to preserve, identify and produce relevant information. This includes identifying appropriate limits to discovery, including limits on custodians, identification of relevant subject matter, time periods for discovery and other parameters to limit and guide preservation and discovery issues.

Disagreement between counsel on where to draw the proportionality line is to be expected because the premise of proportionality is some agreement as to the true value and importance of the case. This requires counsel to discuss both liability and damages in a realistic, non-posturing manner. Even non-binding agreements based at least in part on these core issues can be very difficult at the beginning of a case, but not impossible. For instance, all early mediation and case settlement depends on some common parameters beyond posturing as to case value. In especially difficult or contentious cases the early use of a mediator or special master to help the parties reach basic agreements on how discovery will be conducted can realize substantial savings over the rest of the case.

The U.S. District Court for the Northern District of California suggests that proportionality be discussed and includes this on their ESI checklist for use during the Rule 26(f) meet and confer process. Section six of the Checklist states:

IV. Proportionality and Costs
☐ The amount and nature of the claims being made by either party.
☐ The nature and scope of burdens associated with the proposed preservation and discovery of ESI.
☐ The likely benefit of the proposed discovery.
☐ Costs that the parties will share to reduce overall discovery expenses, such as the use of a common electronic discovery vendor or a shared document repository, or other cost-saving measures.
☐ Limits on the scope of preservation or other cost-saving measures.
☐ Whether there is potentially discoverable ESI that will not be preserved consistent with this Court’s Guideline 1.03 (Discovery Proportionality).

The referenced California Guidelines for the Discovery of Electronically Stored Information at 1.03 states:

Guideline 1.03 (Discovery Proportionality). The proportionality standard set forth in Fed. R. Civ. P. 26(b)(2)(C) and 26(g)(1)(B)(iii) should be applied to the discovery plan and its elements, including the preservation, collection, search, review, and production of ESI. To assure reasonableness and proportionality in discovery, parties should consider factors that include the burden or expense of the proposed discovery compared to its likely benefit, the amount in controversy, the parties’ resources, the importance of the issues at stake in the action, and the importance of the discovery in adjudicating the merits of the case. To further the application of the proportionality standard, discovery requests for production of ESI and related responses should be reasonably targeted, clear, and as specific as practicable.

The key to proportionality discussions is the non-binding nature of any concessions made, and a general staged-approach to discovery, starting small, without waiver of rights to ask for more discovery, or to object to later discovery. Again, quoting Judge Nolan in Kleen Products: [T]o the extent possible, discovery phases should be discussed and agreed to at the onset of discovery. Parties should at least be able to reach an agreement as to how the first stage of discovery will be conducted and defer for later discussion any additional discovery that either side may seek. Phasing is also included in the California Checklist.

The proportionality discussions should also apply to the parties preservation efforts. See The Sedona Conference® Commentary on Proportionality, October 2010. This is specifically mandated by the California Guidelines at 2.01(b):

In determining what ESI to preserve, parties should apply the proportionality standard referenced in Guideline 1.03. The parties should strive to define a scope of preservation that 2 is proportionate and reasonable and not disproportionately broad, expensive, or burdensome.