There are a few principles that I am pretty certain are always true.
Firstly humans just have a instinct to communicate and share knowledge. Look at the millions of bloggers out their who produce sites without any real profit?
Today companies should be aware that their staff is twitting and posting much of what they learn at work. Staff naturally wants to capture and share the narrative of their lives because they are creative and social beings by nature.
Companies that don't provide a place for this internally will see information leaking out via twitter.
This is probably one of the key reasons to roll out a large and pretty open SharePoint internally. It gives staff a place to put what they learn with their own colleagues. People will always prefer collaborating with people they have regular contact to over just twittering to the Universe.