I remember hearing about this a few months ago. I looked it up and it's a rather interesting idea, in my mind. As a general rule I dislike funerals and most of the rituals people go through for death. My family was pressed into an elaborate open-casket funeral and evangelical speech when my grandmother died. The reason was that it had been her express last wishes for how her death be handled, and noone really cared about it enough to disrespect that desire or the other family members.
Redardless of this, I do believe that most people psychologically require some way of dealing with the death of someone they know and care for, and I don't feel that there's anything wrong with that. The desires of the corpse-to-be should play some part in this, as should the friends and family's. If turning a person into a handful of diamonds works, then why not? If they want to be fired out of a cannon, go for it. Mummified? Sure.
Short version: I don't find this any more ridiculous than any other act it would replace/augment.
"I hate to advocate violence, drugs or insanity to anyone, but they've allways worked for me." Hunter S. Thompson