sequential check if single point is within polygon VS multipoint intersection with polygon

gistfile1.py

# ------------------------------------------------------------------------------
# this works fine (finds correct amount of objects within an area)

# walk all areas
for area in areas:
    polygon = ogr.CreateGeometryFromWkt(area.polygon)
    within_count = 0

    # walk all objects
    for obj in all_objects:
        point = ogr.Geometry(ogr.wkbPoint)
        point.SetPoint(0, obj.lon, obj.lat)
        if point.Within(polygon):
            within_count += 1
            
    print "{0}: {1}".format(area.name, within_count)


# ------------------------------------------------------------------------------
# this doesn't work (misses objects, although they are within area)

# create multipoint of all objects
all_objects_multipoint = ogr.Geometry(ogr.wkbMultiPoint)
point = ogr.Geometry(ogr.wkbPoint)

# walk all objects
for obj in all_objects:            
    point.SetPoint(0, obj.lon, obj.lat)
    all_objects_multipoint.AddGeometry(point)

# walk all areas
for area in areas:
    polygon = ogr.CreateGeometryFromWkt(area.polygon)

    # intersect to get amount of objects within area
    intersection = polygon.Intersection(all_objects_multipoint)
    within_count = intersection.GetPointCount()
    print "{0}: {1}".format(area.name, within_count)