A few weeks ago, I erased and reinstalled my iPhone software (iOS 5.1). I also decided to jailbreak it right around that time.
Since then, I've noticed that several of my contacts have the wrong information in my phone. Mobile numbers (and in one case an email address) are sometimes off by one digit/character, or two digits are swapped.
For example, if my contact's phone number is 555-0391, I will discover (after sending a few texts to a complete stranger) that her number is actually stored in my phone as 555-0319. A few days after I've fixed the number and obsessively checked to make sure it's still correct, I notice that it has changed again, this time to 555-8391.
I'm totally willing to accept that this is a case of user error, but I just want to check to make sure this isn't a known issue, being caused by a sync bug or malware, etc.