Would that sum the entire column in the spreadsheet? But what if I wanted to have a couple tables on a page (which I often do), or my sum below the numbers?

see my post above.

if you use insert row - then formulas respond and will go from C2:C10 to C2:C11 (tested in excel2003 at least)

This is probably useful in many cases, but one could imagine where the inserted row bisects other ranges in other columns unintentionally.