I tried inserting the following document:

{
"_id" : ObjectId("510c1f0a9dcaa36340e0c983"),
"location" :

{ "type" : "Point", "coordinates" : [ -122, 37 ] }

,
"friend_ids" : [
123,
456
]
}

Added the following index:
db.updates.ensureIndex(

{ friend_ids: 1, location: '2dsphere' }

)

But when I query for the following, nothing is returned:
db.updates.find({ friend_ids: 123, location: {$near:

{ type: "Point", coordinates: [-122, 37]}

}})

It works for non-array fields. Is this by design or a bug?