When a new Earth-crossing asteroid or comet is discovered, it's orbit is rarely known with any great certainty. The cross sectional area of the Earth divided by the area of space the object might possibly pass through yields the chance of a collision. With each successive night of observation, the orbital characteristics are determined to greater accuracy, and the cone of potential trajectories is reduced. As a not-so-intuitive result, the reported probability of a doomsday scenario grows geometrically higher with each successive night of observation. In some cases it makes national or world-wide news as the probability of mass extinction grows from 1 in a billion, to 1 in a million, to one in 10,000... Obviously there's a trend there, right? Some journalists think so, then mass hysteria ensues and NASA receives correspondence from mothers asking if they should euthanize their children to protect them from the horrific event (a true story, sadly).
Then at the height of mass hysteria, the next night's observation brings the circle of uncertainty just small enough to exclude the passage of the Earth, and instantly the probability of Armageddon drops to zero. Those media outlets who hyped the doomsday scenario then accuse the scientists of fear mongering (ironic), and the public forgets until the next big object is found looming our way, and the cycle continues.
It's sad, but not unexpected that the general public lacks the mathematical literacy to understand these statistical quirks. It's truly sad, and perhaps even criminal that journalists, and especially science journalists fall victim to those same misconceptions.