The other place not yet mentioned where this gets even more important to consider is when you use a table-valued function within a CROSS APPLY clause. It's in those cases where it sets up something like a "correlated sub-function".
Again - very powerful potential, but will tend to quickly turn into something not at all efficient on the execution plan side.
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?