There are MANY oppinions of who could be the mole and why. Most say Artemis, some say Miss Martian or Superboy. Most of the talk about the mole has been spread across the other blogs. Here's one where they can all fit.
I think Miss Martian could be a mole for the white martians. Season 2 is named 'Invasion'. She may also be a mole for the light because of Queens bee's threats against her.
Artemis' father is a member of the the shadows which are employed by Ras', who claims there is a mole on the team, as does Sportsmaster.
Superboy could be telepathicaly sending information to genomorphs without knowing it. Cadmus was founded by Lex Luthor. There is also supposed to be a big battle and Superboy has his sheilds.
There's more but I'll leave that to you guys.