Ok, going to the original post...
I agree, to people who have lost loved ones (and lets face it, who hasn't) the idea that they still exist in some manner of speaking and are being looked after, can bring immense confort, and you cannot deny that from anybody.
You pointed out that it can't be very comforting for athiests when people die, believing that we all just got into 'dust'. As an athiest, I believe that everything has it's time. Every galaxy, star, planet and human has it's time to shine. Then, one day, it dies, and to quote Steve Jobs 'death is probably the best invention of life'. Without death, life would loose meaning for many people, like myself. The belief that this is your one and only chance, for a lot of people can urge them to contibute something more to life with a greater sense of urgency.
To me, as a scientist, the fact that when we die, our body decomposes into the basic elements that make us up, then goes on to form many other things, from grass and trees, to other people, is beautiful. In a very broad sense, we do live on.
Nothing, no matter how good, should live forever.