See attached patch (based on just released 2.0.0)

(1) Apply the patch to add all time documented but missing in the code parameter "selectMediatypes" for user.get method
http://www.zabbix.com/documentation/2.0/manual/appendix/api/user/get

along with a fix for parameters userids,mediaids for mediatype.get (dummy typo in a table name)
http://www.zabbix.com/documentation/2.0/manual/appendix/api/mediatype/get

(2) Also consider to apply patch to the 1.8 (and also add support of selectMedias from 2.0 to 1.8) or remove declaration of parameters select_medias, select_mediatypes from 1.8 documentation.
http://www.zabbix.com/documentation/1.8/api/user/get

Because it misleads users all these years:
http://www.zabbix.com/forum/showthread.php?t=21042
http://boardreader.com/thread/API_Call_is_failing_any_ideas_why_q2Xhii.html

After patch:

Request:

{ "userids":[3, 7], "selectMediatypes":"refer" }

Response:
"result":[{
"userid":"3",
"mediatypes":[

{ "mediatypeid":"6" }

]
},{
"userid":"7",
"mediatypes":[

{ "mediatypeid":"1" }

,

{ "mediatypeid":"2" }

]
}],

ALL is correct - TESTED