I was a reference for a senior manager yesterday. At first, the reference started to ask me, “What do you think are so-and-so's weaknesses?” I hate that question, because it all depends on the context. And I'm smart enough to turn that question around so a weakness doesn't sound like a weakness. Grr.
But then, the reference asked me, “What do you think it will take for so-and-so to succeed here?”Ah, asking about what it would take to succeed is a great question. (If you're a candidate, ask yourself: What would it take for me to succeed at a company?) Now I have a question I can answer, and we can discuss the issues. I could say, “So-and-so needs an organization that hasn't already made up its mind about everything. They don't need to be totally flexible, but they need to know that there are multiple ways to make the projects happen.” That's not a weakness; it's a statement of how much adaptability the organization needs, and how little so-and-so needs to make the projects successful.
So, when you check references, make sure you ask the question, “What would it take for this candidate to be successful here?” You'll hear much more valuable information than asking about weaknesses.