This is actually an old post (with a newer URL after the site got re-done), but it's worth repeating.
Thankfully, WordPress now no longer by default adds worthless title attributes to every freaking link anymore. But old version still do!
I've seen still too many times "SEO" given as a reason for title attributes. Know this way is pure evil. With all the potential trouble of mis-using title attributes, "doing it for SEO" almost guarantees you are, indeed, mis-using it. And so now you're supporting robots over humans.
The article also touches on the title trick some of us try when the graphic designer insists that the link to the full article is only called "Read more".
As Ryan Benson reminded me, this is one of the big bugs of ZoomText, a popular reader/magnifier.
I'm not sure if an empty-string title attribute is still a problem, but this is certainly code we've been encouraged to use in order to stop Internet Explorer from showing alt text like a tooltip, as it tends to do (however, it should be noted users of IE have come to rely on it as additional information scent, so not sure we really need to remove alt-tooltips anyway...).
A more updated set of recommendations for using title attributes is available at Steve Faulkner's post over at Paciello Group: http://www.paciellogroup.com/blog/2010/11/using-the-html-title-attribute/