We've been doing PPC for several years, and just recently hired another guy to help run the campaigns. He was reviewing some campaigns and asked me "why do we use all of the characters alloted to us? Why don't we see how few words we can get by with?". His thinking was that the white space would attract folks to our ads. It really is good to get some fresh eyes on these campaigns from time to time :)
Obviously this is not new to copy writing, but it never ocurred to me to NOT use all of the text allowed by the PPC sites (since so little is allowed). Long story short, we've been playing with it and we're seeing large increases in our CTR. Results are preliminary, but we're going to increase our spend and see if the results scale.
I've been playing around with a similar technique in that I have one sentence wrapping onto the second line but only having 2 or 3 words on the second line. So far I have seen a small increase but personally I am drawn to the white space in amongst all the other clutter.