Review inflation?

The Chicago Tribune uses the following scale for its restaurant views:

**** Outstanding
*** Excellent
** Very Good
* Good

My first thought was, it's just like grade inflation. Who's going to think a one star review is that of a "good" restaurant?

However, on second thought, I can't think of many restaurants where I've received a truly bad meal. "Nothing special" may be the description of the food at a greasy spoon diner, but the food tastes fine. So maybe the worst restaurant is best described as good.