Contains original blogging flavor!
The headline says plenty: "Fake Blueberries Masquerade As Real Fruit". (The video that is the basis for the article can be found here.)
The short of it is that many products that appear to contain blueberries aren't made with the fruit but rather a combination of sugars, oils, and dyes. Despite what you might simply and reasonably assume, especially from the name and description on the box, you better check the list of ingredients to see if any are actually in there.
To this news I give a big sigh. Life can be busy enough without needing to parse every single little thing to deal with nonsense like this. The box of blueberry muffin mix in my kitchen lists blueberries in the ingredients, so I guess I lucked into that one.