Its official - Google offers search within a site

The Google blog has confirmed that the search within a site option will be offered to users on an increasing basis. To quote from the blog...

Through experimentation, we found that presenting users with a search box as part of the result increases their likelihood of finding the exact page they are looking for. So over the past few days we have been testing, and today we have fully rolled out, a search box that appears within some of the search results themselves. This feature will now occur when we detect a high probability that a user wants more refined search results within a specific site. Like the rest of our snippets, the sites that display the site search box are chosen algorithmically based on metrics that measure how useful the search box is to users.

As per my earlier posts, if you're a site owner that relies on advertising revenue this could have some fairly serious consequences.

You can read the full post at Search within a site: A tale of teleportation