Official Google Blog announced last Saturday that Google Earth has added a new "Geographic web" layer that includes articles from Wikipedia, comments from GE community and photos from Panoramio. See also Techcrunch.
The layer is visible by default, you don't need to do anything. Next time you open Google Earth and zoom into a place, you will see little blue icons from Panoramio wherever photos have been located.
Some people have uploaded photos to Panoramio, but they can't find them in Google Earth. That's because layers are not updated in real time, it might take a couple of weeks.
You can see photos in Google Earth updated in real time opening Panoramio's KML file or at this page.
Since the layer was released Panoramio's traffic boosted. The number of photos uploaded overpassed the psychological border of 100,000 some hours ago.
We want to thank very much everyone at Google Earth Team.