Questions about Azkaban (I'm Behind!)

I finished Prisoner of Azkaban this afternoon and had two questions to put out to the group.

1. On page 204 of the American hardback, Fudge says "Dumbledore, who was of course working tirelessly against Who-Know-Who, had a number of useful spies." We know about Snape, of course, but "spies" implies more than one. Does anyone recall other spies for the Order that have been mentioned? Is there a Death Eater who will turn out to be a spy? I know in Goblet we see captured Death Eaters turning over information, but I don't think J.K. is refering to those people. Who are the spies?

2. On page 370 of the American hardback, Sirius says "Voldemort's been in hiding for fifteen years, they say he's already half-dead." I thought Voldemort would only have been in hiding for twelve years, since Harry was one. Is this a mistake or is there a finer point I've not realized?

What do you all think?