Anyone who has used and seen an iPad noticed that however you hold it there is enough bezel to rest your thumbs on while holding on to the tablet. Apple changed this with the new iPad mini which, while it has enough bezel at the top and bottom, has a reduced edge on the sides with the display going closer to the edges.
Typically, in such a setup and with normal usage, accidental taps should be a problem because, want it or not, your thumb will interact with the screen. However, Apple seems to have thought of that, and instead of making the device bigger by adding to the side bezels they have tweaked the software. “Rethinking the screen meant we also had to rethink the software behind it. iPad mini intelligently recognizes whether your thumb is simply resting on the display or whether you’re intentionally interacting with it”.