Yes, but Niantic reviews the submissions and either approves or denies them. There's a whole section on G+ Niantic setup for handle Portal Appeals (when Niantic denies your submissions, you can post the photo, location, and why you think it should be a portal. Other players can vote yes or no on it, and with enough votes Niantic will review the submission again).
In the end, Niantic (or whoever they hired.. unpaid interns maybe?) are the ones who either approve or deny the portals that go into the game.