I'm working on something similar with the social actions data, and
what I can report so far is that the sweet spot for title length is
about 4-6 words. Hit rates are significantly higher in that range,
and trail off on either side.
Similar to the above, I'm working on lists of individual terms that
associate strongly (in one direction or another) with hit count, and
hope to do that per action source - so you can tell if people
searching by action source have significantly different tastes.
Ehren