Wikipedia definition of extreme sports: The term gained popularity with the advent of the X Games, a made-for-television collection of events. Advertisers were quick to recognise the appeal of the event to the public, as a consequence competitors and organisers are not wanting for sponsorship these days. The high profile of extreme sports and the culture surrounding them has also led people to invent parodies, such as Extreme ironing, urban housework, extreme croquet, extreme unicycling, and house gymnastics.
Wikipedia definition of link exchange: This system was very accurate at gaging the importance of a website when it first started, leading to the popularity of Google.