I just realized my On*Star comment was a bit wordy and contained a lot of
speculation.  Having given it more thought, I think I can reduce my
position to this:

On*Star gives GM the ability to track where you go and listen in on
conversations inside your car.  They can disable your car at will and
probably alter all kinds of parameters we don't know about.

The key question is, "How much do you trust GM?"  Personally, I don't
trust them that much.

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si