Unfortunately for backers of SOPA, Web heavyweights such as Google, Facebook, Reddit and Wikipedia joined the fight against the bill. Sites went black on January 18 to raise awareness. Members of communities such as Reddit put intense pressure on lawmakers (including soon-to-be GOP vice presidential nominee Paul Ryan) until they dropped their support or went on record opposing the bill.

The unprecedented backlash eventually caused supporters to shelve SOPA, and quite possibly ushered in a new age of Web activism.

'Social discovery' apps

If the first wave of social networking was about hooking up with friends, the next wave would be about meeting strangers -- or so the thinking went.

Tech-world pundits predicted a new wave of "social discovery" apps that would change the way we meet people. The basic idea was that, by using phones' GPS, users could see who else was nearby and then meet up with other users with shared friends or similar interests.

"If we get this right, I cannot think of a bigger thing to be working on right now," Paul Davison, CEO of the app Highlight, told CNN in June. "We can take billions and billions of dollars."

Significantly, he also chose not to tell a reporter how many users the app had at the time.

Banjo and Glancee were apps that did something similar. Others, such as Skout and Grindr, were even more specific -- they let you hunt down willing partners for a quick hookup.

But here's the thing -- some users, particularly women, found the apps a little creepy.

OK, so you know that somebody sitting in the same bar as you likes the Pixies, "Firefly," the fantasy stylings of George R.R. Martin and the Atlanta Braves. Are you really just going to start waving around your smartphone to get their attention?

Sure, they've got good taste. But they still might be jerks.

Color

It was supposed to be a tech-world slam-dunk. Instead, it became a cautionary tale about what some feel could become a tech "bubble."

Color, a photo-sharing mobile app, stoked excitement in the startup community that was virtually unrivaled. Before it had a single user, Color had raised $41 million from investors. So certain were its Silicon Valley creators that, reportedly, they turned down a $200 million buyout offer from Google.

With much fanfare, Color launched in March 2011. But users soon complained that the app, designed to share photos with the people around you, often didn't find anyone for them to share with. Its creators were forced to announce they were working on a major overhaul on the same day it was released.

Color tallied about 1 million users at its peak and, more recently, was reportedly down to about 100,000. Compare that to the roughly 100 million users of photo app Instagram (it had about 27 million when Facebook bought it last year), and you see the problem.

Color will be shutting down on New Year's Eve.

Zynga

It reads like an old VH1 "Behind the Music" episode.

"Zynga was riding high. Love them or hate them, its games like "Mafia Wars" and "FarmVille" were everywhere, clogging up Facebook pages and spurring millions of bored casual gamers to pay real cash for virtual cows. Then, it all came crumbling down."

OK, maybe "crumbling down" is an overstatement. But things in The 'Ville definitely didn't go Zynga's way in 2012.

In October, Zynga announced it was laying off 5% of its employees, shutting down its studio in Boston and proposing the closure of others in Japan and England.

(It would be entirely cynical to suggest Zynga hoped to bury that news by making the announcement during Apple's much-hyped iPad Mini event. So we won't suggest that here.)

Facebook, which gets a cut when people spend money on games such as "FarmVille," said that income from Zynga was down 20% over last year.

And, like unskilled mafia warriors, Zynga shot itself in the foot again in March when it bought the company that makes mobile game "Draw Something" for an eye-popping $180 million. But fascination with "Draw Something" dropped off fast. When's the last time you played?