buckworks - 6:47 pm on Sep 7, 2011 (gmt 0)
One major thing that would improve the productivity of Facebook ads would be the ability to limit how many times any particular user sees your ad.
Their "frequency" reports are next to useless, because you have no way to tell, or control, whether your ad was seen once each by a hundred people, or 100 times by a single user who was having a busy session.
AdWords lets you set frequency caps for the display network, and I have found that that boosts the cost-effectiveness of most campaigns. That would be at the top of my wish list for Facebook advertising.