There's lots of interest in the bus ad campaign suggesting that "There's probably no God. Now stop worrying and enjoy your life."
I'm hoping that intelligent observers will have a better grasp of the nature of probability than the atheist advertisers. The statement "there's probably no God" can only be understood as implying that it's more likely that there is not, than that there is a God.
Now there either is or there isn't a God. If there is a God, there either are or there aren't ways to substantiate God's existence; and whether or not there is a God, there's certainly no way of substantiating God's non-existence. On this rather crude analysis you might make a case against that 'probably,' but not with any great interest perhaps.
You can look, like Clifford Longley, at discussion of scientific indications of a 'deliberate' universe, like the fine tuning of various parameters. This is interesting, but it seems to me that this doesn't really cover the question of probability.
Practically, the overwhelming proportion of humanity that believes in some kind of god seems a possible line. "Most of the world is probably wrong," would hardly have made a catchy campaign, though it might have led to interesting discussions.
But personally I think the sentence "there probably isn't a God" simply isn't meaningful. It looks grammatically fine, it just fails to function as a proposition.
My own reading of the ad, then, is
Some atheists neither believe in God nor understand the basic concept of probability. Not to worry. Even in credit crunch Britain adult education is widely available.