Same bug. Here was my report to apple. Awaiting (but not expecting) an answer
Summary: iPhone keeps resetting this setting... "settings" > "safari" > "remember cookies" , it should say "always" which is what I set it to. However, it every day or so will be magically set back to "never". I think this is obviously a bug since a setting that doesn't stay set is abnormal. Furthermore, the impact is that any website which requires cookies functions abnormally. (logins don't work, sessions are forgotten, even the apple website won't let you log in).
Steps to Reproduce: Use my phone, doesn't happen to my wife's phone. Happens to a couple coworkers' phones. The action is toe set "settings" > "safari" > "remember cookies" to "always". Then use the phone for several days.
Expected Results: Returning to "settings" > "safari" > "remember cookies" will not have changed.
Actual Results: Semi-frequently it will.
Regression: Didn't used to happen. Been on iPhone with the same settings/synchs since my iPhone 3gs on iOS 3. Used that until iOS 4.x. Then bought iPhone 4s and upgraded to iOS 5.0.1 and have been having this problem ever since.
Notes: This occurs with or without synching. I have iCloud enabled, and tied to my ***** email address with Apple.
Removed my email from the bug report copy