Spending or Wasting Time on Web 2.0 Tools?

I just read a couple interesting posts: The Pursuit of Busyness - by Andrew McAfee and The Enterprise 2.0 Hawthorne Effect and Enterprise 2.0’s Productivity Perception Paradox by Joe McKendrick.

Andrew McAfee raises an interesting dilemma about the use of Web 2.0 tools (ex. Wikis, Social Bookmarking) in the Enterprise:

people who use the new tools heavily -- who post frequently to an internal blog, edit the corporate wiki a lot, or trade heavily in the internal prediction market -- will be perceived as not spending enough time on their 'real' jobs

This is almost the inverse of the concern that Nick Carr brought up soon after the initial E2.0 article came out -- that busy knowledge workers wouldn't have time for the new technologies.

It's something I've somewhat wondered about. Do people have enough time to use these tools? If so, does that mean that they are somehow not the people who are already "too busy" at their jobs? Are the only people who will use the tools exactly those people who the organization views as time wasters, tinkering about, etc. I think most of us can relate to that kind of concern.

Joe summarizes this concern wonderfully -

That is, won’t employees spending time on the Web checking out Web 2.0 and Enterprise 2.0-related tools and sites be perceived as not spending enough time at their “real” jobs?

If we turn this towards the world of learning and performance, I'm afraid that we may already be suspects in the pursuit of things that are not our "real jobs."

I wonder how hard it is for people to justify spending time on these new technologies, new ways of learning and collaborating?

I'd be curious to get thoughts on this?