When updating a host, there is no validation whether the domain exists [if it does not exist, it is ignored - instead of throwing domain does not exist]
Steps to reproduce:

Via Hammer:

hammer -d host update --name <<server.fqdn>> --domain-id 1935

hammer -d host update --name <<server.fqdn>> --domain-id shlomizadok

both return Host updated.

Via Api:

Started PUT "/api/v2/hosts/smartproxy.local.lan" for 127.0.0.1 at 2014-11-12 09:25:35 +0200
Processing by Api::V2::HostsController#update as JSON
  Parameters: {"host"=>{"domain_id"=>"shlomi"}, "apiv"=>"v2", "id"=>"smartproxy.local.lan"}
...
Completed 200 OK in 368.9ms

Expected result:
Return an error "Could not update host"
Example:

hammer -d host update --name smartproxy.local.lan --medium-id 232134

Returns:

DETAIL:  Key (medium_id)=(232134) is not present in table "media".

Could not update the host:
  ERROR:  insert or update on table "hosts" violates foreign key constraint "hosts_medium_id_fk" 
  DETAIL:  Key (medium_id)=(232134) is not present in table "media".