It looks like at least one reason this tomato plant was not doing well was nematodes.
Interestingly there was a large marigold plant right by it. Marigolds are known to deter nematodes but I am guessing the garden would need to be filled with marigolds before planting tomatoes for this to be effective.
I might try filling the garden with marigolds and see how that works out next year.
There is a Celebrity tomato in the same garden which is in much better condition. When the plant is done I will take a look at the roots to compare. Celebrity tomato plants are said to be resistant to nematodes, verticillium wilt, fusarium wilt 1 and 2, and the tobacco mosaic virus. You will see letters by the name of a plant, such as VFFNT for celebrity, which indicate what the plant is resistant to.
See here for an explanation of what the letters mean: http://forums.gardenweb.com/forums/load/tomato/msg0410215232107.html