Stanford's Clifford Nass has spent his career showing that people respond to technologies not as inanimate objects but as people. Our mental machinery evolved for interacting with other Homo sapiens, and when we approach a computer, a service, or a piece of software, we're still tapping the same circuits. We even like praise from machines -- just think about how ludicrous that is for a minute.
All this to say: People have relationships with the social networks they use. When Twitter used to go down every other day, it felt like being in a "She's just not that into you" romance. One minute she was there for you. The next minute, there was just a flying whale's vacant eyes staring back at you. You refreshed and refreshed. "Did she get my message?!" you wondered. You refreshed again. Finally, she would return and your heart would Tweet.
Now, the new hot young thing is Tumblr. In the past year, the site's seen incredible growth thanks to its hip design and ease-of-use. The site went down Sunday afternoon and stayed down until late Monday. This service outage drove Tumblr users, who also tend to be web power users, crazy. As one media site put it, the "Internet freak[ed] out." There were rumors that EVERYTHING WAS LOST, and lots of mumbling about database clusters. The outage even spawned it's own single-serving site called, WhenTumblrIsDown.com.