From David Lewis at IUPUI:
This article argues that academic libraries should commit 2.5% of their total budgets to organizations and projects that contribute to the common digital infrastructure need to support the open scholarly commons. This level of contribution is necessary if the needed infrastructure is to be put in place. Establishing this level of contribution as the expected norm will help to create the incentives necessary for individual libraries to make contributions at this level.
Source: The 2.5% Commitment