We have some free community events, such as 1 Million Cups, wherein the organizers find it extremely important to receive credit for their work. Does this signal a problem?
Community managers are usually fairly modest, without egos. But that said, everyone wants to feel appreciated from time to time....receiving credit for work done is one aspect of that. I think it's a matter or "credit, in moderation"
Given that recognition is the only form of payment, why wouldn't they want that credit when the event is a success?
Keeping their light under the barrel is not effective. As a high level civic volunteer for 6 years, I can tell you if nobody knows about what you did, you basically didn't do it.
Different people are motivated by different things. Recognition can be a huge motivator for individuals, and if it's lacking, they'll run out of gas for the project. Conversely, if they feel they're getting noticed, they will put even more effort into it. Make use of that.