Chip joining has been tried, but with poor results, and I do not think that this is exactly what Dalsa is doing; I think that they are joining several "stepper images" on a single chip.
An early ill-fated Minolta DSLR really had two chips side by side, but a special prism arrangement was needed to split the image, since there was inevitably a gap between the chips, too big to fudge over with firmware tricks.
Still, all the talk of joining and firmware adjustments at the edges and such make me prefer to stay with sensors small enough to be cut from a single piece of cloth, so to speak. It is bad enough that Trinitron style monitors have one or two thin but annoying lines across them!
