Facebook traffic inside enterprises has continued to fade according to Zscaler’s latest State of the Web report for the first quarter of 2012.

The application remains the biggest single source of web application traffic among Zscaler’s customers at 41 percent, but this is down from over 52 percent in the first quarter of 2011.

Although not dramatic, the fall in the application’s presence among the company’s user base has been steady, dropping around 2.8 percent each quarter.

No other application appears to be getting more popular in its place - although Twitter has risen slightly to 7.2 percent – which raises the likelihood that Facebook is simply being more carefully managed.

“A significant reason for some of the declines in enterprise social networking transactions is corporate policy, meaning that enterprises appear to have been increasingly limiting access to Facebook but have been less concerned about Twitter,” note the report’s authors.

“Zscaler has noticed a general upward trend in Twitter traffic over time, suggesting that it is becoming a more widely adopted resource for employees as a broader range of people have begun leveraging the service.”

Other popular web applications include LinkedIn on 18.2 percent, Google Search on 8.3 percent, and a range of webmail services on a few percent each.

Extrapolating Facebook’s traffic decline beyond Zscaler customers would represent a bit of a stretch. As the company points out at every opportunity its user base is able to block Facebook and other web applications by policy thanks to the company’s technology – not every company will have access to such a feature.

What Facebook’s decline suggests is a greater interest in controlling social media applications if that possibility is available.

According to Zscaler, the two main restrictions on web use – 83 percent of the time - are limitations placed on bandwidth and specific categories of website. The remaining 17 percent is the long tail of social media enforcement and policies to cope with instant messaging, webmail, malware and spam.