IPhone :: Does A Jailbreak Affect/harm ITunes Backup Data

I am a perfectionist, and I am curious. Once, a little while ago, I jailbroke my iPhone 3G (somewhere in de OS 3 saga). I was quite surprised by some new features and I kept the jailbreak for a while. So I got texted, my call history extended et cetera.

But for some reason I wanted to get back to Apples pure, not modded, OS. But I still wanted to have my SMS history and Call History et cetera. On quite a few forums I read about an easy DFU mode and restore with the latest backup I made within iTunes. Written at those forums was that no jailbreak data was backupped in iTunes. Of course, this was a normal backup in iTunes, but from a jailbroken iPhone. I did my restore and my iPhone worked quite well. In fact it still does perfectly, with all histories and logs, in iOS 4.0.1.

But my question is: is there still some data in my iPhone right now from when it was jailbroken, tranfered with a backup created when it was jailbroken? In other words: does a jailbreak affect/harm a usual iPhone backup in iTunes in any way?

So, do I still walk around with some weird strings in my iPhone, or some 0's and 1's in some file?