Facebook in an Enterprise: Weird Thought Or an Untapped Potential?

I was in a meeting with my existing ECM customer last week and during the course of our discussion we picked on a very interesting subject, Social Media in an enterprise. The CEO of this multi-billion dollar company had assigned the task to his IT manager to study the possibility and adaptability of implementing social media solution in the company.
For a moment i thought the CEO wants to increase social media presence of the company, since though he runs a large company, but that enterprise is not very known to people outside the industry domain and naturally a CEO would be interested to increase the brand value of the company by putting-up a brand building campaign on social media networks which might help him to increase the share value of company (that's the only thing every CEO is concerned about all the time :)). But I was wrong, the CEO wanted to bring a social collaboration culture within the organization, which doesn't just rely on information exchanged through email or posted on the intranet portal.
So what does the modern day CEO wants? Well, he wants a true social collaboration culture within the organization just like we use Facebook to keep in touch with our friends. He knows that today a working professional spends maximum time of his life at work, with the colleagues in office and we need to socialize at work. So can the organizations allow professionals to socialize the same way, they socialize in their personal life? Or it has the risk of decreased productivity?
There is enough push from collaboration solution vendors for the use of social media in an enterprise and there is enough resistance/opposition from within the organization. Microsoft has been increasingly making noise about the social media features in the upcoming SharePoint 2013 and I just happen to attend a webinar from HP on Autonomy social collaboration features. So what does an organization really wants? Do they just want people to be more proactive in sharing information with each-other and communicate more effectively, so there is a 'social' angle to it as well.
If it just about the communication platform, I am not sure how is it going to be difference from various intranet portal which organizations have developed over the years which also provide features of blogging and an internal Wiki. But if its about the 'Social' angle, then I am wondering as where does SharePoint or Autonomy provides a 'social' platform, just like the one provided by the super-successful Facebook.
That's where my weird thought takes place. Why don't we think or Facebook CEO, Mark Zuckerberg think that Facebook can be a great social media platform even for enterprise. In short, any organization's expectations from an internal social media platform would be the same, wherein the staff can post the information and people interested in that information can 'like' it to build their own cluster. People can create discussion threads and they can be archived as a corporate records. Organizations can build and deploy various apps for the users to support various business processes, and the list be long.
One of the greatest challenge faced by organizations today is poor response from end-user for the new technology deployment. This is the universal truth that the human-being is naturally resistant to change and managing change can be really painful exercise. But  do we think that people will resist in using Facebook at work? Well, if the answer is NO, then there can be a big YES from many organizations in the world, who would like to contact Mark for building a "enterprise version" of Facebook :)