Effectiveness or lack of effectiveness more like!! It is measurable alright, but disappointingly ineffective. CTR's of 0.04% can hardly be viewed as effective. Much lower than Google Adwords results.
It appears that Facebook users are so busy communicating with each other they have no time for the little advertising boxes on the right hand side of the screen, even though they do have images instead of just text. Perhaps the members of Facebook may notice a huge moving banner placed by MSN for millions of euros, but I doubt they will be clicking away from their conversations with friends, so it may give uplift in brand awareness but unlikely to result in action taken by the Facebook users.
It appears that I am not alone in my observations, Valleywag.com also wrote about this issue back in 2007, Reachstudents.co.uk also cited appalling CTR's in November 2007, Tradebit.com in May 2008 and how to split an atom in October 2008.
These blogs and media sites, were also quoting CTR's of 0.04% back in 2007, my ads have not performed any better, despite testing different copy and countries and target groups and tweaking the ads. Is this like the Google AdWords phenomena where effectiveness has also tailed off as more and more advertisers have jumped on the band wagon.