The problem is there were no revenue forecasts in the S-1. And the subtle change in the S-1 language wasn't an adequate basis for all the analysts to revise their revenue forecasts.
The analysts discussed their own forecasts with Facebook and the result of the discussion was that they lowered their numbers. Companies subtly make their discomfort known if analysts put out numbers they don't think they can beat. See http://dealbook.nytimes.com/2012/05/22/facebook-i-p-o-raises...
And, since the forecast changes were made with Facebook's implicit approval or at least without Facebook's objection, clients who received those updated forecasts got information from Facebook which was not available to the public in the S-1, or elsewhere.
The analysts discussed their own forecasts with Facebook and the result of the discussion was that they lowered their numbers. Companies subtly make their discomfort known if analysts put out numbers they don't think they can beat. See http://dealbook.nytimes.com/2012/05/22/facebook-i-p-o-raises...
And, since the forecast changes were made with Facebook's implicit approval or at least without Facebook's objection, clients who received those updated forecasts got information from Facebook which was not available to the public in the S-1, or elsewhere.