A couple of colleagues and I were just talking about this earlier this week: Why do certain vendors make it so hard to find technical information on their products? The cynic in me says it is because they have something to hide. Product complexity. Complaining customers. Open support cases. Some vendors don’t want you to see that kind of stuff until after the deal closes. But does anyone really expect to find communities with 100% customer satisfaction and no open support cases?
I always thought IBM/Lotus did a great job with this and they still do. The old notes.net site is now under developerWorks. User forums are completely open. Technical documentation is freely-available. There are more learning resources than you can shake a stick at. And most are available without a login.
For open source, it goes without saying that the strength and openness of a community is an important factor in technology selection–without that you wouldn’t even think about implementing in production. In the closed-source world, I agree with Tony–for big vendors and small vendors alike, it makes sense to do some homework as part of your due diligence.