... for example, in a digital camera, a tablet and a cellphone, all of which have cameras on them and will be storing images on the card.
I'm asking not from a mechanical standpoint (assume the card will not be damaged in moves from one device to the other) but from a software one. From my understanding the common DCIM directory should appear with its subdirectories for each of the devices, and they should not interfere with one another's data.
Apart from filling the card to the very top, which should be avoided judging from some of the answers here, are there any other pitfalls which might result from this approach?