After some user requests we have implemented a tag cloud in Panoramio. We waited until there were enough tagged photos in Panoramio to make the tag cloud useful and attractive. There is nothing more disappointing than a tag cloud with few, irrelevant and biased tags.
However once you reach a certain point the tag cloud may encourage people to tag their photos in order to make them easier to find. We still don't have the posibility to search by tag, but we will try to do it as soon as possible.
Btw, we have also included pagination for user photos and comments, also a long overdue feature.