The biggest risk we've identified with rolling out any new collaborative tools is in actually getting people to use them. People are creatures of habit. Unless you make it just as easy or easier to do things the new way, people will continue to do it the old way, even if there are benefits to the new way.
As I noted earlier, blogs provide a natural knowledge capture mechanism if you can get folks to actually change their work habits to include posting to a blog instead of hammering out an email. David, our resident curmudgeon on this issue, makes several points to this effect in his response.
Will people worry about their "proprietary knowledge," or will they see a reduction in the number of times they have to answer the same or similar questions? Is our corporate search good enough to find all this information? Can we automatically maintain a feed directory? Are there RSS tools that corporate users will readily adopt? Do corporate policies actually inhibit use of these tools? How easy is it to integrate an RSS feed into our standard intranet sites?
We hope to address all of these questions and more with a proof-of-concept over the next couple of months with a handful of IT groups that work closely together. These will be internal blogs, but it should be as easy to post to them externally as it is to write an email on your work account when you are home.
I'll let you know how it progresses.