I like the styrofoam or plastic bowls a lot because they work pretty well for things like small portions or little snack bowls for parties or what have you, and they're discardable. Realistically, when I use them at home, I tend to wash them and re-use them for light duty stuff so I feel a little less guilty about tossing away something that's not really going to degrade for a very long time, so the eco-friendly option seemed like a good thing to try.
Apparently they're made out of potatoes, corn and limestone. They're microwave save, and "soak proof".
Okay, I think that last phrase might be reaching a bit. I tend to think of "soak proof" as something akin to "dishwasher safe", or "washable", or something like that. In any case, I kind of expected that putting a liquid into the bowl might be okay.
Turns out the bowls dissolve in water. Well, not immediately. There's a surface coating that seems kinda like a thin plastic film, and if it gets punctured, it allows water into the inner "foamy" part, and that dissolves like those cornstarch packing peanuts that look a lot like unflavored Cheetos. Unfortunately, the film is rather easily punctured. Possibly even by passing cosmic rays.
So putting soup into said bowls would be a bad idea.
Just in case you might want to try this on your own.