If you need to hire fast, there are ways to get the group to be effective quickly. If you normally work on long projects, it could take a long time before everyone gets a chance to interact, debate, reach conclusions and pull together to deliver. So, why not get everyone together and run a mini-project over a few days - a sharp, intense, end-to-end experience which really forces people together to debate, conclude and deliver. That can really accelerate the group's transition from forming/storming into norming/performing.
I absolutely agree. Test mini-project is probably the best way to see person in action. No tests, recommendations or anything else can assure that person will actually fit your team.
The opposite of this, of course, is groupthink...
It's also part of this. Groupthink is a danger regardless. Either you're all trying to appease each other so no one tries to have different ideas or stand out, or you're all friends so no one with different ideas lasts.