It might have always been this way, but Flickr is making some odd choices when paging their photos. As you can see in the screenshot, it stacks the photos in three columns, but only completely fills the first two, leaving an empty slot in the last column.

Ive tried this with several different searches, different ordering, etc, and it appears to be random. Sometimes it completely fills up the grid, sometimes it leaves one space, sometimes it leaves two. The first time I saw it, I thought my search only brought up one page of result, but then saw the pager at the bottom, along with the number of results.

I dont know what they are thinking, but its odd. At least to me.