(CNN) -- Christina Cimino was logging onto Twitter on Thursday morning when something happened that she found deeply unsettling.



iReporter David Seaman says Twitter needs a competitor so users don't panic when it goes down.



"I got some weird error message, and I'm like, 'What's going on!?" the 24-year-old said.



That error message was the scourge of online social networkers worldwide on Thursday as cyber-attacks shut down Twitter and caused sustained glitches in other social-media sites like Facebook and the blogging site LiveJournal.



Twitter co-founder Biz Stone wrote the sites were the victims of what "appears to be a single, massively coordinated attack." And a pro-Georgian blogger, whose accounts on Facebook and Twitter reportedly were the targets of the denial-of-service attack, told CNN the online strike was timed to coincide with the one-year anniversary of the Russia-Georgia conflict.



What may prove more lasting about the day social networking suffered its first major blackout is the degree to which people cared. Near-panic erupted in some corners of the Internet as people lost cherished links to their online friends, family members and news feeds. Watch CNN iReporters talk about the attack



Part of the panic relates to the sheer popularity of the sites.



Twitter saw a more than 1,300 percent jump in unique visitors between February 2008 and February 2009, according to Nielsen NetView. The site, which lets users post messages of 140 characters or less, had more than 44 million worldwide users in June, according to comScore. More than 120 million users log onto Facebook at least one time each day, the site says.



To be sure, not all Facebook and Twitter users freaked out because of the attacks. Some people even reveled in the mayhem. Blog: Could the attacks be our fault?



But for people like Cimino, who said she "felt naked" without access to Twitter, the attacks were a serious reality check -- a chance to evaluate just how dependent they'd become.



"You know how you pat your pockets for your cell phone and your keys? Well it's that same kind of phantom [limb] with Twitter," she said. "It's like, 'I can't update! I can't update!' It's just one of those bugs that gets in you."



She added: "I was pretty upset, actually. It feels like a lifeline for me ... Pretty much everyone knows almost every detail of my life by what I'm doing on Twitter."



It's not worth analyzing whether these online connections are good or bad because the reality is that Twitter and Facebook are now an important part of our lives, said Marc Cooper, a journalism professor at the University of Southern California's Annenberg School for Communication.



"For many people, and not just young people, the Web is not just media, it's actually a place where they conduct their lives or a portion of their lives," he said.



"So the panic [Thursday] morning is only reflective of that. This is not just a hobby or an amusement or another accoutrement, it's actually deeply woven into their lives and is integral to their social interaction. So when it's cut off, it's a problem."



Others saw Twitter's existence as the problem and relished the chance to make fun of a Web site that has become so omnipresent in news cycles.



"Horrors!!! People will have to communicate face to face!" one user commented on CNN's SciTech blog.



Another commenter said, "Turn off your computers and read a book or get outside and discover there is more to life than cyberspace. The Internet has become nothing more than the new cocaine."



Now that Twitter is back online, the No. 1 conversation thread on the site is called "whentwitterwasdown," where users discuss what they did without their real-time Twitter updates.



Some people are mocking the blackout. A user named PaulWilks, for instance, wrote, "I took
What social media sites went down in the article? What were the sites victims of? Who were the victims of cyber-attacks? What were the social networks victims of? What day did the sites go down? When did Twitter and Facebook go down? When did the sites go down? What did one Twitter user say she felt?
Twitter "appears to be a single, massively coordinated attack." Facebook and Twitter a single, massively coordinated attack." Thursday Thursday Thursday naked"
question: What social media sites went down in the article?, answer: Twitter | question: What were the sites victims of?, answer: "appears to be a single, massively coordinated attack." | question: Who were the victims of cyber-attacks?, answer: Facebook and Twitter | question: What were the social networks victims of?, answer: a single, massively coordinated attack." | question: What day did the sites go down?, answer: Thursday | question: When did Twitter and Facebook go down?, answer: Thursday | question: When did the sites go down?, answer: Thursday | question: What did one Twitter user say she felt?, answer: naked"