I posted a photo of a damaged tomato to Facebook asking "What's eating this tomato?", and was quickly given the likely culprit.

It appears that most people believe it's worms, and most people have faith in Sevin Dust.

The first result in a quick online search brings up the Tomato Hornworm.

The Hornworm, they say, can decimate a tomato crop in a very short amount of time, so it's important to keep an eye out for them or for damage to the leaves or the fruit.

A few ways to try to prevent Hornworms include: tilling your garden at least a foot deep prior to planting (this will churn up the Hornworm cocoon); plant fragrant herbs or flowers intermittently with your tomatoes (basil, dill, marigold); and wasps. Yes, wasps. There are some wasps that are parasitic: they lay their eggs on the worm's back and then the larvae eat into the worm, eventually killing it.

Anyway, I'm still learning about gardening and I saw this damage on a friend's tomato crop, so I wanted to be in the know before my garden develops the same issue.