From the Libpub Google Group discussion: https://groups.google.com/forum/#!topic/libpub/Gbb_qtRPClY
Here is an overview of the pros and cons of working with content aggregators, and some tips on what to look for in an agreement with a vendor. Ultimately the choice has to be up to the editor or board of each journal and will depend on a number of factors, including the subscription model, intended audience, and goals of each journal.
Journal will receive additional exposure through discipline-specific database (and in some cases multiple databases that are owned by one vendor) that might be subscribed to by University libraries, who, depending on the journal, would likely be their target audience. This would increase the journal's exposure, that they might not otherwise get through other avenues such as being harvested through WorldCat, DOAJ, or another Open Access Index.
It is good to have content available through many channels and this may mean having it available through the aggregators, which contain lots of non-OA content.
The database service may provide enhanced metadata that then become associated with their journal. The quality of the subject terms is, of course, up for debate. The vendor should also be willing to provide statistics similar to something like Google analytics, noting the amount of times articles have been viewed, and so forth. Some indexing and abstracting services claim copyright over the metadata found in their databases.
Potential for revenue through royalty payments
For content that is not openly available elsewhere there is the opportunity for revenue based on usage in the vendor's database. Amount of revenue may vary widely depending on a number of factors, including scope and timeframe of content in the database, whether or not the content is available elsewhere, and overall size of the database in which the content appears. Journals should clarify these issues and ask for a royalty estimate.
Since these vendors provide access via subscription-based databases, some OA journals may find it misleading that they aggregate OA content alongside subscription-based journals.
Vendors may be unwilling to link from the vendor site directly to the OA version of the article, or let users know that the journal content is available openly.
What to look for in a vendor agreement. Questions to ask.
Read the fine print.
Do not sign exclusive agreements unless you are being paid (handsomely) for exclusivity.
Check the term length of the contract and whether it is automatically renewable, or allows you to re-evaluate after two to three years.
Ask for a royalty estimate. Those checks vary widely in size, and a vendor ought to be willing to both provide an estimate and explain how royalties are calculated. Will the royalties be affected by having the content openly available elsewhere? Similarly, the vendor ought to provide usage statistics.
Make sure the vendor isn't sub-licensing your content, or that you have some sort of control over where your material shows up. Many authors get upset when they see their articles appear on Amazon at $5-10 each.
Ask for references. The vendor ought to be willing to put the editor in touch with other editors that are happy with the service.
Find out what data is required from the journal and at what intervals. Do you need to provide article-level metadata in a useable format, or a copy of a PDF of each issue sent to the vendor? What mechanism will be in place to provide metadata and content to the vendor, and will this be a "push" or "pull" model? How much work will this require on the part of journal staff or other journal partners?
Will vendor provide link back to the journal homepage or individual articles?
Michigan Publishing: Agreements between a publishing partner and a content aggregator
Contains information about points for journals to consider when deciding whether to allow journal content to be aggregated.