Take a second to read this abstract from Tseng et al.
“Specifically, members with knowledge-seeking motives to participate in online brand communities became committed via two routes: with or without symbolic motives. On the other hand, entertainment-seeking members became committed only via the route through symbolic motives.”
Essentially, people that came for knowledge became committed to the community if they were satisfied with the knowledge gained and, to a slightly lesser extent, if they became motivated to be socially integrated with the group.
People that came to the community for entertainment become committed only if they became first motivated to be a part of the group and then, sometimes, to achieve a positive distinctiveness among that group.
On a model, it looks like this:
The key lesson should be obvious. Determine first if this is a community where people want to be informed or to be entertainment. Promote that purpose. Once people join, focus messaging and activities towards either ensuring they learn effectively (knowledge route) or gradually feel a great part of the group identity (entertainment routes).
Sounds obvious, but then you might be surprised how many people get the two confused.