[rabidrat]

If you can't give a 100% positive reference, tell the person before they include you as a reference. Then when giving a reference, make sure it is 100% positive.

Google (and in fact, most companies) only want to hire candidates who appear flawless. To me, "appears flawless" is a red flag itself, but I think hiring committees see any potential negative as possibly the tip of a terrible iceberg. So even though we all want to be honest and provide nuanced feedback about what it was like to work with a person for years, when giving a reference you just need to censor all of that and pretend like they are the best person you ever worked with and the only downside is that you're not working together anymore (but you'd hire them back in a heartbeat).

It's like talking with a reporter or the police. Stop trying to be helpful to anyone but the people you already know. Strangers are not to be trusted with your inside information, about anything.

[cozos]

What about when they ask "what is this person's biggest weakness"?

[ohyes]

They’re too nice and they work too hard.