MathOverflow + Math.StackExchanage are great resources for learning and talking about mathematics. Often, I can get constructive and informative discussions leading to progress.
MathOverflow is a web site for experts, but what happens if I have a question that is graduate-level but outside my field of expertise. I have gotten down-votes for misusing the terms in a field which I never had a chance to learn. And that point, I don't even know if my terms are incorrect or well-known.
This could create a dis-incentive to be curious and could hinders people in different fields from talking to each other, or learning something new. Sometimes, we are brought to this area naturally by research in another area where result $X$ is not very well-known. And the things experts consider "new" can be somewhat surprising.
Or conversely, can I only ask question on MO in areas where I am already an expert?