I like looking for great definitions for concepts that people have a lot of confusion or disagreement on. The Internet of Things is definitely one of those terms that qualifies.
I like this definition based on the switching role of the computer and the functionality.
So in the past we had cars with computers in them. But now a car is a computer that takes you places. We used to have phones with computers in them, but now your phone is a computer that makes phone calls.
In an IoT world, everything is a computer—the question is just one of form factor and purpose.