Hail? Or wind?

Slugs?

I'm having the same problem. Some of the leaves have had so much disappear from them in this way that half the leaf is gone.

Here are some pictures of my older tomato plant that has suffered the most. I have younger seedlings growing now and I want to see if I can figure out what this problem is so I can stop it from effecting them as well. I have already noticed some of my younger plants developing this problem.

Hail! Have you had any?

I agree with Jean - most likely hail or strong winds. Any strong thunderstorms lately? That's the usual cause.