Ran into an issue with the current iOS7 release with contacts, and figured I’d share.
The other morning my contact list was wiped. No contacts. But contacts were on my Mac. I sign into iCloud and all my contacts are there (and Apple did a GREAT job with the iCloud contacts page, you should really check it out).
I realized that one of my Exchange accounts had its password expire and I hadn’t set a new password. Creating a new password and putting it on my iPhone restored all of my contacts.