While this role is most definitely necessary, I've found it's no fun to be that person, even when others value the dissent.

I've voluntarily taken on this role in the past when I've joined a company or project where nobody else was shooting down bad ideas or playing devil's advocate. After a while it feels like you're always on defense while others are bringing ideas to the table.

But of course those are minor issues when the alternative is every crazy idea making it past the filter, and someone's got to do it.