The Yahoo Search Blog announced yesterday a new crawler behavior for the newly trained Slurp (Yahoo's search crawler). So instead of Slurp running around your site like an untamed animal, it is not more proper and polite.
I looked through the forums yesterday morning to find people discussing any ranking or traffic changes seen at Yahoo but came up with nothing.
Now, however, people are buzzing a bit about traffic changes seen from the Yahoo Search referrer.
One person saw a drop in traffic:
I just ran through some of my results page ranking for Yahoo and man-o-man have I taken a nosedive. Looking through G-Analytics its as if my site ceased to exist on Yahoo on August 18th.
An other person saw a huge spike in traffic:
I don't know if it's significant... but my Yahoo traffic quadrupled today and now outstrips my Google traffic. I don't know if it's a blip but it appears to be an improvement in traffic from Yahoo across the board and not from a few specific keywords.
Typically the forum threads come before any official Yahoo "weather report," but in this case, they came in after.