When this whole CarrierIQ thing got started, I thought this was simply a diagnostic tool, yet conspiracy theorists were going to jump all over the "...but they could" aspects of the system. I also thought it was a shame, since the carriers and manufacturers ought to be able to monitor the system so they can improve it.
Your post has made me re-think all of my notions. I don't believe any nefarious purpose was afoot-- this was a tool intended to diagnose infrastructure and device performance. However, installing it as a rootkit is a bad call. It provides a vehicle for malware, and a description of its operation-- however technically accurate it migh be-- touches too many evil buzzwords. Such a tool, while useful, is eventually too easy to turn into a PR nightmare (obviously). Then throw the malware hijacking aspect in for good measure.
Verizon does it right, at least as we see it now. Those vans do a great job of real-world testing, where their test equipment is gathering the same metrics as CarrierIQ's software, but with test data nobody will whine about.