Facebook’s advertising machine is growing fast, and it’s growing big: estimates put 2011 ad revenues at some $3.8 billion. But it’s also a system that is always being tweaked as the company tries to turn its vast trough of users into more cash.

The latest changes, you may remember, are an attempt to convince advertisers that they should be focusing on engagement more than click-through rates — what Mathew characterised as an appeal to “forget about clicks”. From the outside, it may be difficult to understand why this matters — but here’s some data that might shed some light on what Facebook is doing and why advertisers love fan pages so much.

Courtesy of social analytics firm Campalyst, we have information on a campaign run for Blue1, a Finnish subsidiary of Scandinavian Airlines. Through August and September, Blue1 ran a campaign across three different channels: a Facebook page with regular status updates; Facebook ads targeted on potential customers; and more traditional display ads.

Here’s what they found: branded fan pages — and the updates that users see — are vastly more successful than other ways of advertising on Facebook....