Yesterday, I reported at Search Engine Land that Google is going to allow cross domain canonical tag. This means, if you have two sites (probably verified under the same webmaster tools account), you will be able to tell Google, all links pointing to domain A should point to domain B.
Clearly, this is a feature that is really something many webmasters and site owners have wanted for a while. At the same time, some webmasters are scared that this can be hacked into and you can lose your whole domain. The bottom line, Google will make sure to make this secure as possible, before releasing it.
Currently, the canonical tag is only to be used within the same domain. So this is a major change to the tag.