The godless move in mysterious ways: what the atheist bus campaign’s advert will look like. Ariane Sherine: All aboard the atheist bus campaign - guardian.co.uk
I would add:
1. Why are they advertising – what benefits will they get?
2. The presumption that the there is no-God will lead people to enjoy their life is flawed.
3. Advertising is usually used to propagate or open up a perceived need in the person who sees the advert. This does not to that.
4. Surely the most powerful thing that leads people towards the non-existence of God is simply that many don’t really think about it. This campaign forces people to think about God!
Here’s a billboard advert I found that was quite fun.