ok, we know orochimaru was with akatsuki soon after leaving and he would have a pretty good idea of what the group is about and their goals.
now many would guess that the group is gathering jutsu (as jiraiya said) and that they are looking for alternate sources of chakra, such as the kyubi. each member has their own speciality and abilities, the sharkfin has his samahada sword which is extremely powerful, itachi. . no need to elaborate, and the only other member we know is orochimaru. he left, he said, because itachi was more powerful then him. there might be more to it then that but i think his obvious goal of immortality leads him to need more independecne then the group would allow. now there are higher echelons in the group, but that doesnt mean those are more powerful then itachi. maybe they are senior and at that level everyone is so damn powerful it doesnt really matter.
he was interested only in sasuke during the 2nd test, and ignored naruto, bothering only to seal him. he then later tries to kill naruto because he fears that akatsuki might get him and do god knows what with him. i really dont think even orochi can do the rasengan.
doesnt it seem odd that orochi would want to kill naruto only after seeing that? i think that akatsuki might have a plan for naruto that we dont really understand yet (other then just getting the kyubi from him) and since orochi is trying to build is country's power . . seems to be a bit of a hole here in orochi's behavior. of course he is a powerful madman who would kill anyone on a whim but still. he is more calculating then that.
