Interesting to see some criticisms of the social theories of CoPs because they make sense. Rather than blame the person or the CoP, better to understand the issues. This paper addresses some important issues, particularly addressing online CoPs ability to be a real CoP.

1 prescriptive versus description distinction
This is a very important point that Wenger is misinterpreted. You can nurture and support a CoP but you cannot design or take a cookbook approach. CoPs are about content not form.
2 ready-made versus communities in the making;
People make their own CoPs. They will form their own subgroups if you try to design or control a CoP and the conversation on the side may be counterproductive, particularly if their is a profit goal, a power differential or an ethical issue at foot. Ignoring interpersonal relationships is unwise and fantasising that relationships are all productive and collaborative are just not true just because you design it that way.
3 knowledge of possession versus knowing in practice;
Can you really learn without doing. Can you really have a knowledge only CoP and thus an online CoP is not practice based so is it a CoP?
4 mid-level social theory versus micro learning theory; and
Both models are required
5 motivated members versus unwilling subjects.
Can you morally coerce someone to share and give and collaborate. Will you be able to do it? Will they sabotage?What kind of motivation.? Is internal motivation more likely to result in collaborative behaviour than externally motivated?

Reference

Schwen, T. M., & Hara, N. (2003). Community of Practice: A Metaphor for Online Design? The Information Society, 19, 257-270 Retrieved Googlescholar, 21/12/2007
http://scholar.google.com.au/scholarq=ethics,+communities+of+practice&hl=en&lr=&start=10&sa=N