For one, all your incentives and permissions in W2.0 environment are focused on the individual. In Facebook or twitter, the concern is who do you connect to? who can see your info? who do you follow? and so on.

By contrast, in the enterprise, content is organized around groups, projects, or departments which may see individuals come and go. Take an engineering team – the lead users may leave the company as a new crop comes in. The content “belongs” to the product line as much or more than to the individuals who authored it.

How about a consulting company doing a customer case? An expert may be brought into a customer case blog for just long enough to contribute. After even a short period, the expert may be blocked out of the continuing conversation.

With respect to the security related differences, see

I’ll agree that data will become more accessible and activities of all sorts will become more transparent as network effects are realized to be more important than privacy (or simply hoarding) benefits. But the way we get there in the Enterprise may borrow some principals from W2.0, while being careful not to simply clone it.