Here is the total uptime (in percent terms) experienced by the popular social networks for the period Jan 1 2008 to April 30 2008:

Twitter : 98.72%
Reunion : 99.35%
Pownce : 99.44%
Bebo : 99.51%
Hi5 : 99.55%
Live Spaces : 99.67%
LinkedIn : 99.74%
Friendster : 99.76%
Last.fm : 99.79%
Orkut : 99.90%
Facebook : 99.91%
Classmates : 99.92%
MySpace : 99.96%

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