If there are other systems / information out there that are already performing the function that you need then there's no need to reinvent the wheel. That just causes fragmentation throughout the web; something that doesn't benefit the user in the grand scheme of things.
For example, take a site about film reviews. If they're discussing the film and want to give you further information about the cast and crew would it make more sense for the site owners to do all the research into the crew, post links about each member who worked on the film and supply a little biography about them on their own website and have to manage and maintain all of that information locally, or would in make more sense to use a source that has already acquired and provided that information - IMDB? That movie site owner isn't going to be able to provide a better source of information than IMDB already does, so why spend time and effort making a substandard clone of it? Heck, IMDB even provide API support for just this reason - they've got a wealth of useful information and provide the ability for anyone to use it.
Another example is why sites like Github exist - if someone has needed to create something to perform a specific task then the chances are it's already been created. So why do it again yourself if someone else has already done so?
So I see this as a similar situation. Why reinvent the wheel with something substandard when there are already great implementations that have solved the problem already there and available to you?
Don't create something like a forum just for your one product in an attempt to retain ownership over it. You can't own knowledge and knowledge kept to a small set of people will stagnate. If there is already a system in place with a good community then just jump in there - share the knowledge and learn something more in the process.