I kind of like the idea of a god with a dark sense of humor and a keen eye for irony. Like this: All the atheists and agnostics go to the afterlife and the big G says “You know, you guys never found any concrete evidence for the existence of all of this supernatural stuff and I can respect your search for the truth, even though you wound up wrong. For that, I’m going to tell you the secret of the universe and give you everlasting happiness”. To the true believers from whatever religion that wind up in the afterlife he says “You had absolutely no tangible proof whatsoever that any of this existed. You simply nodded your head and followed the other sheep, bleating about ‘faith’. As I gave you a functioning brain and expected you to use it, I simply cannot abide by that sort of mindlessness. Therefore, I will grant you everlasting happiness, but as you don’t seem to value a true search for evidence of the underlying nature of the universe, you don’t get to learn the secret of it all.”
Dr. Joan Bushwell's Chimpanzee Refuge 
Interesting concept, but would (e.g.) Francis S. Collins be let in on the secret? There are plenty of others, but Collins certainly has faith AND explores the universe.
Looked at the other way, in my experience there are plenty of sheep-like atheists – if blindly following someone else’s lead disqualifies you from knowing the ‘secret’ what would God do with them?
All good points, but as it was meant as a humorous aside…
If this is Yahweh we are talking about, you can bet that the secret of the universe has a lot to do with someone else’s genitals. :D
What if I already know the secret? Would god have another tidbit for me?