Some flaws, obviously. Like, if the site is owned and operated "by Christians, for Christians," they will all be long gone six days after the Rapture. The computer can't know it's Rapture time unless it's told, so someone who's "left behind" has to be around to push a button. Either that, or one of the operators has to be around to push the button once they know Jesus has descended. Or they could set up a Shabbat Goy-type person, who is a non-believer, to make it happen. but how are those zealous believers going to avoid witnessing to that button-pusher to get the hell out of dodge before the end of the world?
And what's to stop the Anti-Christ from pulling the plug on the whole operation before the Second Coming?
However, there is also The Post-Rapture Post, a website created by an atheist computer scientist to assist those who believe the end of the world is at hand. For as little as $4.99 you can have a final hand-written message hand-carried to the recipient of your choice. For such a low price, it will take two to six weeks for delivery. Here's a sample of the additional personalized cards it sells --
Aren't You Afraid of God's Wrath?
We don't believe in God, remember? In the event that the Rapture actually occurs, we will go to Plan B: "Lifetime of Sin Followed by Deathbed Repentance."