It is an interesting function guide. The idea could be very useful in helping people learn different functions.

A couple of suggestions.

1) You might include a section or discussion on "relative and absolute references." Especially with lookup functions like this, where you will usually want your "lookup_table" argument to be an absolute reference, but your "lookup_value" argument to be relative. You might include a "what happens when we copy/fill this formula down into B20:B23.
2) I noticed that your lookup table just happens to be sorted on column 1. I entered the formula using TRUE as the fourth argument. It marked me "wrong", with its expectation that one would use FALSE for the fourth argument. I could see real value in having examples that show the difference between TRUE and FALSE in the 4th argument, and how to actually use those differences.
Along those lines, another example might be where someone wants to search in "ranges". If lookup value is 1 to 10, return "a", if 11 to 20 return "b", and so on. I see a lot of problems on the forum that could be simplified if people understood how these "binary" search algorithms basically worked. In your example lookup table, you could use searches on "date" as a way of illustrating how this works. A lookup value of "7/1/11", with the 4th argument FALSE returns N/A, because that date is not in there. But, with the 4th argument TRUE (and the dates sorted in ascending order as they are), it can find the value for 6/23/11.