Apple’s Pages word processor tries to be clever and anticipatory. When you create a table, by default cells in it are created as spreadsheet-like cells, rather than the text format that you might expect from a word processor. Furthermore, the type of the cells is “automatic”; that means that it waits until you type, and then determines what type to apply based on that.
I’ve just been using this for student marksheets. Interestingly, if I type a mark like 3/5 it “automatically” assumes that you are typing a date, and converts it to “3rd May 2013”. If you type something like “30/50” it assumes that you are typing a vulgar fraction, and converts it to “0.6”.
This seems to fit into the “too helpful” area of HCI failures.