I have multiple sites across my company that are not connected via a single network and have standalone AD Forest's in place. I would like to setup a hosted Exchange / SharePoint / OCS solution for all the sites allowing the users to use their current AD credentials. I also would like to avoid consolidating the domains into 1 forest. Can I use AD Federation Services to do this? Are there any drawbacks to this in Exchange, SharePoint, or OCS? I would like to have a single GAL if possible.