Have you used Google Docs collaboratively with another person? While I type, I see what you're typing.

If you instead use Excel files stored on the network, and you and I want to "collaborate" on a document, at best we're ping-ponging the file back and forth to each other. Sometimes we collide, and have to Merge - which is very painful if we've made any kind of extensive changes.

Suggesting Sharepoint / SVN is a reasonable solution to how to collaborate is like suggesting one telegraph system over another. It's not remotely the same thing, at all.

Office 365 is much better, granted. But the SkyDrive interface is no better (and in many ways worse) than Google Docs.