Quote Originally Posted by Crash
Kabuto would actually make a lot of sense. Orochimaru was Sasori's original partner and Kabuto is Oro's right hand man so it's very possible that Kabuto would have had some contact with Sasori. Perhaps Kabuto was hoping to get back into Akatsuki himself by helping Sasori.
Ah, forgot about that. Now we actually have a reason as to why Sasori put a spy on Oro, other than him being an Akatsuki traitor.

Quote Originally Posted by Abdula
I don't think Kabuto has any aspirations beyond serving Orochimaru, he reveres him on the level of a deity.
Don't forget, Sasori had a technique that locks the spy's memories, making them indeed very loyal to their master, only for their memories to unlock, and their loyalty to return to their true master. That's how they tricked the Sand. Up to this point, Kabuto may have well been loyal to Oro, though at one point in the Chuunin exam arc, he did seem a bit fishy.