The Devil's Advocate is a regular staffer in most offices. "Let me play Devil's Advocate" is a socially acceptable way to shoot down an idea. It's a guise that allows anyone to criticize an idea without offering an alternative. It's far easier (and safer) to tear down than to create. You can undermine what someone has just proposed without actually challenging them directly.
Sometimes we need someone to see the bad side of an idea. How it will be mis-interpreted. How it will be abused. How it will conflict with other initiatives.
But first we need a team who will look for the good, will brainstorm the possibilities before everyone (or is it just the same someone?) starts taking shots at it.
Are you the one who plays Devil's Advocate? Are you a permanent nay-sayer? If so, please stop.