In 1910, the appearance of Halley's Comet led to an outbreak of popular fear. Astronomers had recently discovered that the comet's tail contained the deadly gas cyanogen - and the earth was expected to pass right through it. People fearing cyanide poisoning bought gas masks and "comet pills" to protect themselves. Of course, nobody died (well, possibly someone choked on one of them).
Today, we have our own madness over Comet Mcnaught, with it variously being mistaken for a "an object falling from the sky" and a plane on fire - leading to calls to the fire service and police. You'd think the fact that it wasn't moving might signal to people that it wasn't anything of the sort - but apparently not.
Meanwhile, I've finally seen it (despite the clouds), and it is indeed magnificant. Halley in 1986 was just a fuzzy blob, wheras McNaught is quite spectacular. It's not a patch though on some of the Great Comets I've been reading about, which had tails stretching 90 degrees or more across the sky. Something that big and bright seems to come along every 25 years or so, so there's a good chance that I'll be able to see one in my lifetime.