If there's one thing the digital revolution has taught us, it's that we shouldn't get too attached to anything. Technology has a way of seizing long-held ideas and entrenched industries and turning them upside-down.

Disruption is rarely the result of a single gadget or innovation, however. It's typically when two or more technologies converge that the real changes start to happen.

For this look at the most disruptive high-tech events of the last quarter century, we divided developments into pairs that have formed an effective one-two punch. On the following pages are our picks for the ten technology duos with the biggest impact.

10. DVRs + Entertainment on Demand

Remember programming your VCR to record TV shows? Of course you don't, because nobody did it--the task was too difficult and time-consuming.

Fast-forward to the late 1990s and the introduction of the TiVo and ReplayTV digital video recorders. Time-shifting programs and fast-forwarding through commercials became as easy as pressing a couple of buttons. Suddenly people were no longer shackled to the arbitrary schedules of TV programmers and the obnoxious pandering of advertisers. Cable and satellite providers rushed out their own DVRs, and millions of folks began "TiVo-ing"--even those who had never touched an actual TiVo.

Like the best disruptive tech, DVRs returned control to users--and made consumers hungry for even more control over what they watched, when, and where. In 2005 the Slingbox introduced place-shifting, making it possible to watch your TV (or your TiVo's content) over any broadband connection. Later that year the video-enabled iPod sealed the deal, and broadcast content was permanently untethered from the tube.

Though iTunes' video library was far from comprehensive, it proved that if people get an easy alternative to file sharing, they will pay for what they want. Today, video-on-demand services--including ad-supported ones like Hulu.com that are owned and operated by the broadcasters themselves--are booming. Thanks to TiVo, iTunes, and other similar advances, we now expect our entertainment to be delivered to us wherever we are, whenever we want it, on any device that's handy.

Disruption: The whatever/wherever/whenever model of media consumption is turning both Hollywood and the consumer electronics industry on their heads, and forcing advertisers to rethink ways to capture our attention.

9. YouTube + Cheap Digital Cameras and Camcorders

One word: macaca.

When the candid video of former US Senator George Allen calling someone a macaca (a monkey) appeared on YouTube, it not only cost him a Senate seat and altered the balance of power in the United States Congress, but it also demonstrated how far viral video had come. The Web is now the first stop for many political candidates and companies trying to spread the word about themselves or their products, and YouTube accounts for more than 60 per cent of all video-site traffic, according to Hitwise.com.

YouTube wouldn't have reached such heights without cheap digital cameras, camcorders, and mobile phone cameras. Several key developments led the way. For example, in 1995 Sony introduced the first digital video camcorders with a FireWire (IEEE 1394) port for high-speed transfers to PCs and Macs (cost: US$3000). NEC built the first cell-phone cameras that could capture streaming video in 1999. In 2006 JVC introduced the first digital camcorders to record directly to hard drives.

Now, of course, palm-size camcorders can be had for less than US$200, and streaming-video capture is a standard feature in most cameras and camera phones. In fact, the first Pocket Film Festival was held in Paris in October 2005--with the winning entries posted on YouTube, naturally.

Disruption: Digital video has made mini-Hitchcocks of everyone. YouTube and its many cousins give the masses a place to put their masterworks. Journalism, politics, and entertainment will never be the same.