Displaying items by tag: bad data

A recent poll on Mashable purported to show that users prefer real books to e-books.

Looking at the poll, it's pretty clear: people overwhelmingly prefer real books to e-books.

However, if you take more than quick glance, it reveals its lack of depth. The question had three choices: prefer books, prefer e-books or happy with both.

On the face of it, those seem like valid questions - so what's missing?