On one hand, I would definitely rip out anything like onstar, and I would never buy a car that has networking sitting on a CAN bus - that's just terrible; those two things should be entirely separated (or, at most, have very limited contact through just a few hard-coded hard-wired functions.)
On the other hand, I am going to install a remote kill switch and gps tracker into my car.
The only difference is that I trust myself a lot more. Onstar... not so much. And, let's be honest, security by obscurity: I'll be the only one who knows exactly how to track it, how to kill it; someone else can figure it out if they really want to, but they won't have the knowledge by default.