This is something I observed when I switched from 3.8.0 to 3.8.1.
In 3.8.0 when I go to the "find friends from contacts" menu, I have a full list of my contacts (~400 entries or so).
Now, with 3.8.1 the list contains only ~7 entries. At first glance these contacts are some entries in my SIM, BUT not all of them are there though. None of my original contacts are on the list now. This also means, that my already established friends' nicknames do not map to their names in my phonebook, and I lost contact photos. This does not fix itself after a few hours, that I've given to it to sync somewhere in the background whenever it wants to.
Full app+data removal (with waze directory on internal sdcard) with all reboots on the way, and with a fresh install and login/sms confirmation - did not help. The contact related changes between 3.8.0 and 3.8.1 need to be looked at.
One thing that might be different with my setup - I do not store my contacts on the phone, or SIM, or gmail; I have a CardDAV and sync with WebDAV contacts. No other apps are having issues with accessing these however.
Another thing is if the contacts are interated over... if only some of my SIM entries got through, and some contain names like ".something" or "text - text", then maybe some new code fails when processing unusual contact names. Don't ask me why my carrier put these on my SIM...
As a fallback I am stuck with 3.8.0, which works perfectly, but makes no notification sound, when someone shares a drive, etc. Tried to make a workaround for this with Tasker (Notification Event), but these notifications are not caught by it unfortunately.
Other information: Android 4.3 (JB), Samsung Galaxy Note 3.
If you (devs) need more information, please PM and I'll be happy to provide any details I can.