On July 26th the digerati stood befuddled staring at this message:

Twitter's website and the data services that drive its apps were offline, and would not come back on for another two hours.

It wasn't the first time, and it won't be the last. For a site with over 500 million registered users, Twitter experiences notable, noticeable downtime and service interruptions, as it has throughout its 6-year existence.

The strange thing is that these millions of users seem willing to put up with so many technical issues. Twitter's lovers appear to remain loyal, in sickness and in health. Facebook, by contrast, seems not to inspire such loyalty, and most likely cannot afford such lapses in service. It has reached a saturation point in the United States and other Western markets. In fact recent data show that US Facebook user numbers have declined by 1.7% in the last 6 months.

Facebook, Twitter, and LinkedIn are each monopolies: each provides a service that is basically unique and cannot be perfectly substituted by another. Comfort may have led them all some amount of sloth: a survey study called American Consumer Satisfaction Index numbers released July 16th, 2012 has shown that all of them have low "customer satisfaction," higher than airlines but lower than, say, most automobile companies. Despite these numbers, each has experienced rocket-like growth and is clearly doing something right.

If any of these services is threatened competitively, however, it is Facebook. Google's Google+ service was clearly created with Facebook in the crosshairs, providing many Facebook-like features, and awaits with open arms for anyone dissatisfied with the the world's biggest social network. The same ACSI study found Google+ to have consumer satisfaction ratings that, along with Wikipedia, led all social networks. Google+'s top benefits were seen as a focus on privacy and lack of ads, where Facebook was seen to cause privacy concern and ad-annoyance. Out of all the social media networks in the study, Facebook came in dead last.

Don't expect any major changes in the league tables soon: Facebook has achieved its goal of becoming the major "repository of identity" on the internet -- having been baked into many other services -- and its mass-market appeal is strong.

But whereas Twitter's problems appear to be largely technical, Facebook's may be more cultural and competitive. The social media giant will have to work hard to maintain its dominant position. We'll see if Mr. Zuckerberg and Co. are up to the task.

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More good reading:

• Google+ plus announced in June 2012 that they had surpassed 250 million users

• A handy infographic comparing Google+ and Facebook

• For those interested, Venture Beat does maintain a list of Twitter competitors