"It is interesting to see that some of the most popular networking sites turn out to be some of the worst performers," said Mark Pors, CTO at WatchMouse,  a website monitoring service. with thousands of customers in over 70 countries, as he revealed that after WatchMouse monitored the time it took the social networking sites listed on Wikipedia to load, the results showed that the worst, in terms of availability, was the immensely popular Facebook.

"It's surprising that they have gathered such a big fan base when they serve their users so badly. Using AJAX technology, they should be able to work more effectively. I believe these sites will need to do a lot of work to improve their performance if they are to remain popular."

Popular social networking sites are frustrating users, according to WatchMouse - by making them wait.

Pors said that the research shows that Web 2.0 sites often lag behind other commercial sites in performance - they are often slow to open or fail to load properly.

Other well-known culprits included Twitter, last.fm, Windows Live Spaces, Friendster and del.icio.us. Of the 104 sites monitored, nearly half - 51 earned a Site Performance Index (SPI) of 1000 or more, which indicates very slow load time. This was an unexpected outcome, considering most of these sites rely heavily on Ajax, which generally delivers quicker load times because the dynamics of the site do not load immediately. While first generation websites generally required a webpage to fully load each time a user clicked, the use of Ajax helps websites improve interactivity, speed, functionality and usability by instead exchanging small amounts of data with the server upon user action.

Faceparty performed the best - with an SPI of 303 - indicating that users can access the site most frequently and in the fastest time among the monitored social networking sites. Looking at the results, most sites still have a lot to work on if they want their users to keep coming back. Research has shown that most web users are very impatient and will wait no longer than four seconds for a webpage to load. 

A complete overview of the monitoring results of the WatchMouse Site Availability Index, listing all the sites monitored, can be found here.