Okay, having read this and the comments in this thread I'm going to hazard a theory as to what's going on with Kanama and Sosuke and his employers.
It's possible that someone with unpleasant intentions (like the Psi Corps) could grab Kaname and use her as a telepathic back door into the Invid "hive mind" and disrupt, control or otherwise engage in shenanigans with it. Somebody realized this and put Sosuke on the case. It's possible that he was hired by somebody with those unpleasant intentions to keep an eye on her and possibly even make the grab when the time came. Whether he actually would remains to be seen.

Also, I agree with Mercutio's assessment that Akio is using Nanami as bait for the Trinity.

Polychrome

Rampant speculation ENGAGE!