To paraphrase Barry Corbin in WarGames, piss on a spark plug if you think it will help.  Of course you should pray for Hitchens, if you think it will accomplish anything.  Or do it if it makes you feel better, which is what I think prayer is really good for. It doesn't require anything from him, not a signature or thumbprint or even his assent.  It also does not require his knowledge.  And there is Biblical support for always praying in secret: "But when you pray, go into your room, close the door and pray to your Father, who is unseen. Then your Father, who sees what is done in secret, will reward you."  Matthew 6:6.

Another writes:

I was intrigued to read your follow-up post with the cancer expert's empirical data: no effect from undisclosed prayer, but a negative impact from the mockery.  Upsetting an ill person wouldn't seem to be the best prescription for his welfare.  On the other hand, I do think that Hitchens is that rare person with the nerve and strength of conviction not to be adversely affected by such undesired gestures.  Reminds me of the dying Thoreau's familiar response to a friend's intercessionary inquiry as to whether he had made his peace with god:  "We've never quarreled."

Another:

I have cancer.  I found this out 3 weeks ago.  In that time I have grieved like I have rarely grieved.