To illustrate: Suppose you're checking the lottery results online, and you see that you won, and you're on your laptop at the house of a friend who knows what lottery numbers you buy and who has used his wi-fi to play pranks on guests in past. Suddenly the evidence doesn't fare so well against that million-to-one prior.

This reminds me of reading about the Miracle of the Sun (http://en.wikipedia.org/wiki/Miracle_of_the_Sun) in The God Delusion and in a theist's response. I found Dawkins fairly unpersuasive; the many agreeing testimonials weren't enough to overcome the enormous prior improbability, but they were still disconcertingly strong evidence. The theists' response cleared this up by giving historical background that Dawkins omitted. Apparently, the miracle was predicted in advance by three children and had become a focal point in the tensions between the devout and the secular. Suddenly, it was not at all surprising that the gathered crowd witnessed a miracle.

So I'd agree that miracles often have probability of under one in a million, but it's also vitally important to understand the effect of motivation on the likelihood of the evidence. If I thought every testimony to every reported miracle was based on unbiased reporting of fact, I'd have to conclude that many of them happened (caused by aliens messing with us or something).