[el_benhameen]

I think it's definitely supposed to work that way. My first year in my house, I tore out the previous owner's rose garden and planted tomatoes. Had so many that quite a few of them ended up falling off the plants and rotting into the soil. The next year, I scaled my intentional planting back but ended up with even more tomato plants because of the seeds from the previous year's decayed tomatoes. I'm not even going to plant this year, just water and hope that the same thing happens again.

[retsibsi]

I think they were surprised that store-bought tomatoes had viable seeds. I would have been kind of surprised by this too, but a quick google suggests that while some commercial fruit and veg is deliberately made sterile, it's probably much less common than I thought.

[ppf]

The seeds might not be sterile, but you will probably not get the same breed of plant. A lot of mass-produced veg is grown as an F1 hybrid, and the next generation (ie, from the seeds) will not have the same desirable characteristics.

[swapsmagic]

Pretty much every vegetable seeds bought from store are viable, it just for some vegetables (i.e. bottle guard, okra), store bought vegetables aren't ripe enough and so those seeds won't able to germinate. To germinte the seeds of any vegetables, the fruits has to be matures (some times on the plant, sometimes on the shelf) before seeds become viable to germinate. I don't know a single vegetable that will be sterlite. I know some Mangoes (coming outside of US) do get sterlite and so their seeds won't produce plant even if the seeds are mature.

[perl4ever]

Right, folklore was that they aren't viable, and it was before Google.