A comet that was (theoretically) visible from Earth from late 1973 to early 1974, Kohoutek was originally touted as "The Comet Of The Century!" by enthusiastic astronomers who had spotted it beyond the orbit of Jupiter. Normally a comet that can be spotted so far out is extremely bright, and astronomers were expecting a spectacular display, but when Kohoutek actually arrived, it was far dimmer than they had been hoping - almost invisible, in fact, and very disappointing to the tens of thousands of amateur astronomers who had encamped on various hilltops in hopes of seeing it.

It is now understood why Kohoutek fizzled so badly. When compared to the more recent comet Comet Hale-Bopp, which has visited the solar system several times before, Kohoutek was probably a comet making its first trip in towards the sun. This means that it had been surrounded by a halo of carbon monoxide or carbon dioxide which vaporized at a large distnce from the sun, making it flare very brightly. However, when it approached nearer and this halo was gone, it was seen to be very ordinary.

This incident caused great embarrassment to the astronomical community, who subsequently downplayed expectations for comet West, three years later. This actually turned out to be another mistake, as West laid a trail easily visible to the naked eye for several weeks. These incidents only served to remind scientists of how little they really knew about comets and their movements.

Source: http://www.planetary.org/library/gsp-pr-010296-04.html