The forums are starting to buzz a bit about a possible Google Sandbox like algorithm being applied to new sites over at Yahoo! Search. There are two large threads on this topic at DigitalPoint Forums, one here and the other one here. In addition, there is a thread at SEO Chat Forums on the topic. WebmasterWorld moderator Caveman replied to the WebmasterWorld version of this thread stating;
jgbmarc, IMO, there is some evidence that Y has recently introduced some sandbox-like elements to their algo(s). Also, IMO, the so-called sandbox over at G is not at all just about age of sites/backlinks. There are other algo elements that can make it hard for new sites to appear, that have nothing to do with age per se.
It has been eight days since Yahoo! announced this update, I have not really looked or seen evidence for this theory.