[That's something Shikamaru's been wondering himself ever since seeing Itachi as a child. 'He lost faith in his clan. Wanted power; was insane' would be the answers he's grown up with. That he went rogue is the official reasoning recorded on his page in the Bingo Book.

It's surprisingly vague. But these are thoughts for another day.]

I don't know. But the fact is he did, and he's done more since then. [And it's best not to get into that mess.] I think he's smart enough not to pull anything here. On top of that, he'd have no reason to. Still, it's better to be safe than sorry. If you can't avoid him, at least don't seek him out.