Carrier IQ (aka CIQ, or just IQ) is a market research tool used by Sprint/HTC to see what the phones are being used for. You can find out more about Carrier IQ on their website.
Now there is a huge group of people out there that would tell you this is Sprint/HTC spying on us, and they are right. You can see an example of what type of information is gathered by looking at a sample report from Carrier IQ. It is essentially spyware and is tied in to practically every HTC application on our phone.
This isn't new news and really isn't a secret. Carriers gathering this information helps them see how the phones are being used and how they can improve them in the future. I didn't decide to remove it because I have a tin foil hat on and I'm worried about what they're collecting, although those people will certainly benefit. I chose to remove it because it has a number of services that are constantly running in the background and chew up quite a bit of CPU (and battery) at times.
While I haven't gone as far as to remove the calls to it from every single application on the phone I have completely disabled and removed the service from the ramdisk, the binaries, and the libs. Thus if you happen to be the type that watches logcat you will see some errors saying individual applications can't reach the service. Nothing to worry about.
Despite the fact that I have known about CIQ for a while, I have never chosen to remove it for various reasons. I decided to go for it on Fresh Evo 4.0 because I will be keeping a "beta" tag on this rom until we get some a more official release which means I can try new things.
Questions? Feel free to ask.
Directly from Flipz fresh 4 thread