While RSS still plays a very important role for practically all online publications to get their news out to subscribers, and Google plays a critical role for the stories to get picked up by casual visitors, Twitter is playing a middleman role and growing in the minds of many publishers, who see the microblogging service as a significant traffic driver. Now, instead of using the catchy headlines we once saw in print, or keyword-laden headlines that make Google giddy, we're now seeing headlines truncated to less than 140 characters, or even as low as 125 characters as the standard, assuming a short URL follows.
For me, practically the only driver for the length of a headline is whether it easily fits in one deck for somebody using standard fonts in a browser. I don't tend to think about SEO benefits down the road and don't consider if the headline will "play well" on Twitter or other social networks, but do recognize that a good headline can be "make or break" for those seeing the story downstream, be it through RSS, or on aggregation sites, from FriendFeed to Techmeme or even Digg. (See my post from last year on this topic)
Given that practically every blog is publishing to Twitter in parallel with their RSS feed, the drive to keep headlines short is very real. In my short visit to TechCrunch headquarters on Friday, their tech team said they are very much making sure the headlines play well with Twitter. Their Twitter account now not only shows a headline and a bit.ly URL (for stat tracking) but also the author's Twitter handle, similar to how I've called out posts from other writers on this site with their own IDs.
As Twitter's impact on immediate traffic expands, it should be interesting to see how many blogs change their approach to headlines, and to see if they are in any way reducing longer-term traffic benefits from SEO for instant returns.