Another viewpoint is why ... and how much is necessary?
If a company is doing their job properly, it shouldn't be necessary except in extraordinary circumstances.
BTW, I am not including pre-sales related questions in with my definition of customer support.
I'm not quite sure how to classify the people who buy a product, but haven't graduated from the how to think/read school first though . Fortunately, I very rarely need to deal with that mentality!