Excuse the nerdy pun, but interoperability has been in my thoughts a lot recently.
A big project, unifying the collections of 9 different establishments just failed to get funding after a year of work. We asked the funders why and it came down to the politics. It was just felt to be too hard to get everyone to play nicely together. Sure, when we looked into it, individual data repositories were wildly different and metadata standards had been lovingly honed in isolation over the last 30 years. Melding them into a coherent whole was going to be, umm, challenging, but we knew that all along.
As standards like OAI-ORE emerge, and start to demonstrate how we can move not only data, but objects around the web, we should be entering a period where virtual loans, digital repatriation and unified collections are commonplace.
But we're not there yet.
Because all this is ultimately about people. If we let politics stymie endeavours such as these, scholarship suffers.