Putting your specific question aside for a moment, two community close votes doesn't necessarily mean your question is off-topic: otherwise it wouldn't take five community close votes or action from a moderator to close.
If you see your question attracting close votes and you're pretty sure what you want to know is on-topic for the site, consider modifying your question somewhat to shore up any weak points, or ask in chat or even here on the meta-discussion site for help improving your question so it'll stay open.
Getting back to your question: in general, questions need to demonstrate the necessity of the unique perspective of programmers to answer. General project management questions aren't really a fit here.
While it wasn't flagged, had it been, I would've checked with Project Management.SE to see if it could be migrated, as I think it'd do quite well there. Even though you deleted the question, consider asking it there anyway.
As an aside, this part is a bit bad for the Stack Exchange format:
If so, what would be an example of a successful community managed product backlog, and what are key factors in it's success?
Asking for lists of examples, even if that's just one part of the question, tends to be the part answerers focus on because it's easy. Solid PM question otherwise.