As I was walking through the station yesterday, my eye was caught by the headlines on The Evening Standard, the paid-for newspaper that competes with the various freesheets in London (thelondonpaper and whatever the other one is called). It often annoys me that their headlines give you just too little information. I know that they're not running a public service, but I could do with a newsstand that just told me a few headlines on my way to the train so that I wasn't completely out of touch. I'm not really looking to read a newspaper at the end of a day at work - if I don't have to read something work-related and Duncan and I aren't having an impromptu meeting on the train home - I tend to read a novel to relax.
They obviously do it deliberately to try to encourage people to buy the paper, and I'm sure they have tested different approaches and have concluded that it is better to leave crucial information out than trying to entice people in to reading the rest of the story by giving away a bit more of what it's about.
Using age-old tricks online
In the online world, a lot of the headline writing we do (especially while blogging) is aimed at getting a click rather than a sale, so the barrier is even lower than digging a couple of 20ps out of your pocket as you walk past the Standard newsstand. This should mean that this approach works even better online. Next time you are doing some headline split-testing, why not try failing to tell the whole story?