Perhaps the bean counters out there could compare the cost of carrying large bags of dye (let's say bags equivalent in weight to two passengers?) vs the millions that have been spent looking for just AF447 and MH370. Maybe the numbers don't work - but it seems like they should. Or is it that the airlines would have to pay the cost for the dye, whereas the involved countries are picking up the search costs?
Also - IF it is true that the plane had produced various spurious ACARS messages in the days before it was lost, might that not indicate an intermittent fault in the wiring (perhaps a short) or in the computers?