"banned-players.json" and "ops.json" were wiped out after upgrading to either 14w11a or 14w11b (problem not discovered until after 14w11b loaded, so not sure if it was in 14w11a also).
MC-51144
Upgrading from 14w10c to 14w11b wiped out json lists
Resolved
Duplicate
1
Also experienced the same issue as MC-51116. Editing the UUID's as described in that issue resolved the whitelist problem.