hype cycle
n. A sequence of events experienced by an overly-hyped product or technology, including a peak of unrealistic expectations followed by a valley of disappointment when those expectations aren't met.
Examples
2001
The Hype Cycle was devised by Jackie Fenn, an analyst at the US research firm Gartner Group, to demonstrate what happens when cutting-edge new technologies are introduced.
—Peter Wilson-Smith, “Fund managers take fright over Myners,” Financial News, March 26, 2001
1995
'[Netscape has] browser market share right now,' said Mark Stahlman, a computer industry analyst and president of New York-based New Media Associates. 'They are extremely hot. But we've been in an intense technology hype cycle.'
—Rosemary Metzler Lavan, “Netscape IPO Wows Wall St.,” Daily News, August 10, 1995
1995 (earliest)
Enterprises should evaluate potentially high-impact technologies early in the inevitable cycle of hype and disillusionment, but wait until later to adopt technologies that will deliver only incremental improvements.
—Jackie Fenn, “When to Leap on the Hype Cycle,” Gartner Group, January 01, 1995
Notes
This phrase was popularized by Gartner Group analyst Jackie Fenn, who wrote a report titled "When to Leap on the Hype Cycle" in January, 1995. This was based on earlier work by Howard Fosdick, who coined the closely-related phrase hype curve.

Gartner's hype cycle is actually a five-part sequence:
  1. Technology trigger. A breakthrough, public demonstration, product launch or other event that generates significant press and industry interest.

  2. Peak of inflated expectations. A phase of overenthusiasm and unrealistic projections during which a flurry of publicized activity by technology leaders results in some successes but more failures as the technology is pushed to its limits. The only enterprises making money at this stage are conference organizers and magazine publishers.

  3. Trough of disillusionment. The point at which the technology becomes unfashionable and the press abandons the topic, because the technology did not live up to its overinflated expectations.

  4. Slope of enlightenment. Focused experimentation and solid hard work by an increasingly diverse range of organizations lead to a true understanding of the technology's applicability, risks and benefits. Commercial off-the-shelf methodologies and tools become available to ease the development process.

  5. Plateau of productivity. The real-world benefits of the technology are demonstrated and accepted. Tools and methodologies are increasingly stable as they enter their second and third generation. The final height of the plateau varies according to whether the technology is broadly applicable or only benefits a niche market.
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