Is Facebook this generation's personal phone call?

From what I hear, a few generations ago personal phone calls at work were an action which could bring down the boss' wrath. Nowadays most offices will tolerate the occasional personal phone call, especially with the prevalence of cell phones. However, it seems that Facebook and personal email have replaced the phone call as the scorn of office managers and company bean counters across the nation. As of November 2007 a survey showed that 25% of employers blocked Facebook access and 46% blocked access to MySpace mostly based on the idea that the sites are a productivity drain.

A recent survey of "young" employees found that a third of them would quit, yes leave their employer if their workplace blocked Facebook. Granted, severe internet restriction could be indicative of other environmental problems but still, leaving your job based on browsing restrictions seems a bit extreme.