I love virtuals. They're old, interesting and usually educational. And there will be no more. They can't be adopted and they will eventually disappear from our game. This is to encourage you to get out there and Go get 'em quick!!
There are about 20 Virtuals in Tucson. I have found 14 of those. The others involve hikes I can't do. But I suggest anytime you travel or hit the road, do the ghosties on your map first! Worth it!