This policy is easy for journals to administer, since it can be handled by the copyeditor, and is usually acceptable to editorial board members and others:
"Authors submitting quantitative papers to this journal for review must address the issue of data availability in their first footnote. Authors are ordinarily expected to indicate in this footnote in which public archive they will deposit the information necessary to replicate their numerical results, and the date (such as 'on publication') when it will be submitted. The information deposited should include items such as original data, specialized software, recodes, extracts of existing data files, and an explanatory file that describes what is included and explains how to reproduce the exact numerical results in the published work. Authors may find the Publication-Related Archive of the Inter-university Consortium for Political and Social Research (ICPSR) a convenient place to deposit their data. Statements explaining the inappropriateness of sharing data for a specific work (or of the necessity for periods of embargo past the publication date) may fulfill this requirement. Peer reviewers will be asked to assess the footnote as part of the general evaluative process, and to advise the editor accordingly. Authors of works relying upon qualitative data should submit a comparable footnote that would facilitate replication where feasible. As always, authors are advised to remove information from their datasets that must remain confidential, such as the names of survey respondents."
With the Dataverse Network now operational (Article, project web site), an even easier version of this standard exists, and it has the side benefits of increasing scholarly credit to the author and journal. See below, with more information available here:
"If you have had an article accepted, you should compile a data set containing all data and other information necessary to replicate the empirical results in your article and cite it in your article following the rules at http://thedata.org/citation. You can create this citation automatically, and [if you wish] deposit the data, at the [This Journal] Dataverse (at [This Journal]'s web site). When necessary to protect the confidentiality of subjects or proprietary information, or for other reasons [with approval of the editor], you may restrict access to the data through our dataverse, such as via licensing agreements or fixed embargo periods. No matter how sensitive your data, however, you may not restrict access to your metadata, that is the information which merely describes the existence of your data with a formal citation, and which can also be entered at the journal's dataverse."