This bug exists only in Mongoid 3 (testing on 3.0.15). Mongoid 2 doesn't have the bug.

>> foo = Region.all.cache
#<Mongoid::Criteria
selector: {}
options: {:cache=>true}
class: Region
embedded: false>

>> foo.count
MOPED: 127.0.0.1:27017 COMMAND database=gocheap_test command={:count=>"regions", :query=>{}} (0.4489ms)
2

>> foo.count
MOPED: 127.0.0.1:27017 COMMAND database=gocheap_test command={:count=>"regions", :query=>{}} (0.4392ms)
2

So caching stopped working for counts.