My colleague Jonathan Ginsberg writes about his reluctance to provide legal advice or second opinions by email. After all, he points out, it is our command of the law that is our inventory. Give it away and you go out of business.
I have a more profound reason to approach questions by strangers with caution: I have only the facts that the sender has chosen to disclose for purposes of my analysis. Often, the facts the writer thinks are central are either irrelevant or incomplete. Without all of the necessary facts, my opinion may be fatally flawed.
When I meet with a client, I have an opportunity to ask questions, develop the facts, and look for other pieces of the picture that either support or counter the facts the client has proffered. That back and forth allows me to establish the facts, then offer an opinion that is grounded in the complete factual picture.