Just ran XCode while my iPhone was connected by USB, so I could see the console logs. Webbookmarksd was apparently turned on by the attempted Safari sync.
Here's some of what I'm seeing:
Sep 24 08:47:42 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1358]) <Notice>: (com.apple.WebBookmarks.webbookmarksd) Idle-exit job was jettisoned while dirty. Will respawn.
Sep 24 08:47:42 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1358]) <Notice>: (com.apple.WebBookmarks.webbookmarksd) Exited: Killed: 9
Sep 24 08:47:42 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd) <Notice>: (com.apple.WebBookmarks.webbookmarksd) Throttling respawn: Will start in 10 seconds
Sep 24 08:47:42 Michael-iPhone ReportCrash[1371] <Error>: libMobileGestalt copySystemVersionDictionaryValue: Could not lookup ReleaseType from system version dictionary
Sep 24 08:47:42 Michael-iPhone ReportCrash[1371] <Notice>: Saved crashreport to /Library/Logs/CrashReporter/LowMemory-2012-09-24-084742.plist using uid: 0 gid: 0, synthetic_euid: 0 egid: 0
Sep 24 08:47:49 Michael-iPhone backboardd[52] <Notice>: ALS: SetDisplayFactor: factor=0.0500
Sep 24 08:47:53 Michael-iPhone kernel[0] <Debug>: launchd[1373] Builtin profile: webbookmarksd (sandbox)
Sep 24 08:47:54 Michael-iPhone webbookmarksd[1373] <Notice>: BUG in libdispatch client: kevent[EVFILT_MEMORYSTATUS] add: "Operation not permitted" - 0x1
....
Sep 24 09:03:29 Michael-iPhone ReportCrash[1451] <Notice>: Formulating crash report for process webbookmarksd[1447]
Sep 24 09:03:29 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1447]) <Notice>: (com.apple.WebBookmarks.webbookmarksd) Idle-exit job exited while dirty. Will respawn.
Sep 24 09:03:29 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1447]) <Warning>: (com.apple.WebBookmarks.webbookmarksd) Job appears to have crashed: Segmentation fault: 11
Sep 24 09:03:29 Michael-iPhone ReportCrash[1451] <Error>: libMobileGestalt copySystemVersionDictionaryValue: Could not lookup ReleaseType from system version dictionary
Sep 24 09:03:29 Michael-iPhone ReportCrash[1451] <Notice>: Saved crashreport to /var/mobile/Library/Logs/CrashReporter/webbookmarksd_2012-09-24-090329_Michael- iPhone.plist using uid: 0 gid: 0, synthetic_euid: 501 egid: 0
Sep 24 09:03:30 Michael-iPhone kernel[0] <Debug>: launchd[1452] Builtin profile: webbookmarksd (sandbox)
Sep 24 09:03:30 Michael-iPhone webbookmarksd[1452] <Notice>: BUG in libdispatch client: kevent[EVFILT_MEMORYSTATUS] add: "Operation not permitted" - 0x1
Sep 24 09:03:38 Michael-iPhone profiled[1448] <Notice>: (Note ) profiled: Idled.
Sep 24 09:03:38 Michael-iPhone profiled[1448] <Notice>: (Note ) profiled: Service stopping.
Sep 24 09:04:40 Michael-iPhone ReportCrash[1454] <Notice>: Formulating crash report for process webbookmarksd[1452]
Sep 24 09:04:40 Michael-iPhone ReportCrash[1454] <Error>: libMobileGestalt copySystemVersionDictionaryValue: Could not lookup ReleaseType from system version dictionary
Sep 24 09:04:40 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1452]) <Notice>: (com.apple.WebBookmarks.webbookmarksd) Idle-exit job exited while dirty. Will respawn.
Sep 24 09:04:40 Michael-iPhone com.apple.launchd[1] (com.apple.WebBookmarks.webbookmarksd[1452]) <Warning>: (com.apple.WebBookmarks.webbookmarksd) Job appears to have crashed: Segmentation fault: 11
Sep 24 09:04:40 Michael-iPhone ReportCrash[1454] <Notice>: Saved crashreport to /var/mobile/Library/Logs/CrashReporter/webbookmarksd_2012-09-24-090440_Michael- iPhone.plist using uid: 0 gid: 0, synthetic_euid: 501 egid: 0
Sep 24 09:04:41 Michael-iPhone kernel[0] <Debug>: launchd[1455] Builtin profile: webbookmarksd (sandbox)
Sep 24 09:04:41 Michael-iPhone webbookmarksd[1455] <Notice>: BUG in libdispatch client: kevent[EVFILT_MEMORYSTATUS] add: "Operation not permitted" - 0x1
I am wondering what happens if I remove the iCloud account from this phone completely. May try that next...