Within the last week I performed a similar "experiment" for newly created facebook.com/AmeriStartup. I created two FB mobile advertisements to direct traffic to the website, though the website is more eCommerce/service than any type of sign up. Budget $50 over 3 days reach was ~20,000+; the click through rate was .5% and .4% for the 2 ads; just under 100 clicks to the website with none resulting in conversion. More d…
It was posted on HN a while back. The gist is that there's a high chance that your ad was clicked by click farms, even though you bought it legitimately from facebook (in an effort to fool clickfarm detection, apparently).
What's even more interesting is that not only are you wasting money buying the ads, you also end up with less legitimate "likers" seeing your content because of the way facebook propagates new posts. So you're actually paying to get negative results.