Learned the hard way myself last year. At the end of the season, when the tomatos were 7 feet tall, I wound up having to drive rebar 2' deep and tie to the darn cages to keep them only slightly listing instead of falling over. This year I'm going to use physics to my advantage.
The typical tomato cages are narrow at the bottom, wide at the top. This is a good way to create a high center of gravity. This year, I'm going to get a bunch of 8' cedar fence boards and rip out a pile of 8' long 1 1/4" stakes on my table saw. I'm going to use these and my air stapler to build teepees where the wide part is on the bottom and the narrow part is on the top. I'll stake them in the ground a bit, but with that design, I figure the more weight on them, the more stable they will be.
Or, you can tell me I'm crazy. This is only my second year with the veggie garden.