This integration doesn't just mean loading client apps to access these services. It means understanding that user communications happens over multiple channels today, often for different "aspects" of the person, and both apps and the OS itself need to allow communication through any and all of these. In the Android, Linux, and Windows Phone 7 worlds today, you see "social hub" apps that integrate the streams from these various services in one place. Most are awkward because they don't honor the distinct capabilities of each service but instead present a common denominator (an RSS-like dump).
Maybe someone can design a hub that doesn't have this flaw, but until then I think the better approach is to consider the social networking services more like communications APIs that you enable in apps. From there, let the user call up the service's specific app when he or she wants to engage in that specific social network's full context. That seems to be the philosophy so far in iOS X, though done in a limited way. (A better model is how the RIM BlackBerry PlayBook integrates social context in its Contacts app.) By contrast, Windows 8 seems to be taking the Windows Phone path and providing a hub app, in addition to broader social integration for any communications-capable apps. It's fine to offer a social hub and take the API approach; the mistake would be to focus on just the hub.
With social APIs increasingly native to the OSes, the fabric of communication will grow more complicated, as keeping the various communities in mind for what users share gets harder. That's also an IT nightmare, and the notion of banning Twitter or Facebook will become impossible as such services are embedded into the OS's core services -- another reason for information management approach and an EAS-like standard to make it viable.
The other aspect of this is user privacy -- from hackers, websites, vendors, employers, and other people. We've seen multiple scandals involving companies secretly gathering user information; Facebook is the poster child for such underhanded activities, which is why it is now under a federal consent order, but Google (which has sadly morphed from "don't be evil" to "get mercenary") and Path were both recently caught as well. Several states, such as California, have finally begun to act, and even the feds are now looking at the issue -- after years of complaining that the Europeans were overly concerned on user privacy. The truth is that the U.S. has not been concerned enough, and we now have routine tapping of our private data built into modern services, websites, apps, and operating systems.
It's not clear yet how Microsoft 8 will address such privacy management. Apple already prohibits developers from taking such information without user permission, but after several iOS apps were caught doing so anyhow, Apple now says it will have iOS X seek that permission rather than trust the apps to do it, much as it does with location information. OS X Mountain Lion adds explicit sharing controls to the user's personal information in the updated Contacts app. Let's hope that Microsoft follows suit, and with Apple creates a technology barrier against the likes of Google and Facebook -- rather than restrict the personal information mining to just themselves.
A safer, easier, but more closed environment
An ironic consequence of this move to federated, multichannel, multidevice, fluid-data computing is the increasing centralization of the environments and the control taken by Apple and Microsoft.
When you go iOS X, you put yourself in Apple's walled garden. For iOS, you get your apps only via the App Store, and there are powerful usability reasons to get your media and other content from iTunes. Apple's taken a lot of heat for that gatekeeper approach in iOS, but can point to the fact iOS devices aren't hacked to pieces like the open Windows PCs and Android devices are. For apps, Apple's iCloud syncing works just with iOS X apps, whereas Windows iCloud users can sync only a subset of information: email, bookmarks, contacts, photos, and calendars.
Microsoft's emerging garden is just as walled. For Windows 8 (and Windows Phone 7), as for its Office 365 and SharePoint collaboration services, file syncing and access are essentially limited to Windows devices. Metro apps can be bought only from the Microsoft Windows Store -- the same approach Apple uses. As seen in its Zune campaign, Microsoft has failed to develop a competitor to iTunes, so the path of least resistance for getting media and content isn't (yet) a Microsoft venue. But it may be one day.