One of the issues that just about every large organization faces is system sprawl. Information gets siloed into different applications or even within different instances of the same application. There are a number of reasons for this.  It can, for example, be a consequence of an absence of governance or a dearth of enforcement, but it can also just be a natural consequence of technology marching onward but not necessarily at the same pace in all parts of the organization.  Whatever the reason, information sprawl has a real consequence for productivity — it creates a gnawing daily frustration due to that extra friction when trying to get anything done. Where is what I need? How do I access it? Should I bother to make the extra effort to get what I really should have or is what I have good enough to squeak by? Oh, fuggedaboutit! And this plays out hour after hour, day after day… 
So, what to do about it?  Historically, that has boiled down to doing one of two things: 1) put up with it, or 2) fire-up that big, periodic clean up that requires an army of people, takes many moons to do, and is about as pleasant to navigate through while it is being done as that construction work on the freeway that you passed through this morning on your way to work.  Sometimes that big clean up is an absolute necessity.
But there is a third way to do something about it in many cases. Use your flexible, easy-to-use social platform to be more than just what it was originally intended for. That is, make it work for you as an integration layer. To be sure, this will be more of a “lightweight” solution than going to the trouble of integrating everything into a common source application and/or instance, but holding it all together with social will definitely be much quicker and cheaper.
A good example of information siloing is the infamous SharePoint sprawl problem. People create a SharePoint subsite for, say, a project, which is used actively for the life of the project, but then activity peters out over time. Multiply that by the many different projects and purposes that a good-sized organization will have—dozens or even hundreds—for creating yet another new site. Each of these structures contains useful information to someone. But will those someones ever make use of the information, and, even more importantly, will anyone else? Now, again, this issue can be addressed by a project that combines all of these separate SharePoint libraries and sites into one, or at least a limited number of, portals and that might be the right answer in many cases.
But alternatively, or at least as a near-term solution prior to the bullet being bitten on the grand combining, a social platform such as Yammer can help ease the pain. With everyone in the organization using Yammer and sharing SharePoint files in posts that are available to a wider audience and in an appropriate conversational context, information gets surfaced to the people who need the information even if they have no idea about the source SharePoint structure. As long as at least one person knows where the file lives in SharePoint, what’s in it, and how to access the information, that is sufficient! This approach is essentially crowdsourcing the knowledge of where to get the information that is needed. And in some ways this can be even better than just the brute force combination of information into one big pot because some information in siloed instances actually deserves to stay siloed and not clog up the attention of people. Only the relevant information from the silo actually gets surfaced in Yammer, the rest is mercifully ignored.
So, you thought you just bought social? Nah, you also bought some glue!