Found this when running gdmgreeter under valgrind:

==32442== 144,764 (45,568 direct, 99,196 indirect) bytes in 178 blocks are
definitely lost in loss record 175 of 182
==32442==    at 0x40054FB: realloc (vg_replace_malloc.c:306)
==32442==    by 0xBDFE13: FcPatternObjectInsertElt (fcpat.c:357)
==32442==    by 0xBE07E3: FcPatternObjectAddWithBinding (fcpat.c:514)
==32442==    by 0xBE0CDB: FcPatternObjectAdd (fcpat.c:544)
==32442==    by 0xBDD3F2: FcFontRenderPrepare (fcmatch.c:445)
==32442==    by 0x6C2B48: pango_fc_font_map_load_fontset (pangofc-fontmap.c:1081)
==32442==    by 0x819C9F: pango_font_map_load_fontset (pango-fontmap.c:107)
==32442==    by 0x6C2E54: pango_fc_font_map_load_font (pangofc-fontmap.c:1140)
==32442==    by 0x819D28: pango_font_map_load_font (pango-fontmap.c:64)
==32442==    by 0x818228: pango_context_load_font (pango-context.c:272)
==32442==    by 0x81DEE5: pango_layout_line_get_extents (pango-layout.c:3882)
==32442==    by 0x81E1EE: get_line_extents_layout_coords (pango-layout.c:2028)
==32442==    by 0x820D44: pango_layout_get_extents_internal (pango-layout.c:2129)
==32442==    by 0x821C6C: pango_layout_get_pixel_extents (pango-layout.c:2267)
==32442==    by 0x821D59: pango_layout_get_pixel_size (pango-layout.c:2338)
==32442==    by 0x85DB26: gnome_canvas_text_set_property (gnome-canvas-text.c:1089)
==32442==    by 0x7C4BBD: g_object_set_valist (gobject.c:694)
==32442==    by 0x86AF2F: gnome_canvas_item_construct (gnome-canvas.c:291)
==32442==    by 0x86B036: gnome_canvas_item_new (gnome-canvas.c:203)
==32442==    by 0x8053A42: greeter_canvas_item_break_set_string
(greeter_canvas_item.c:637)
==32442==    by 0x8055924: greeter_item_size_request (greeter_geometry.c:533)
==32442==    by 0x80555A4: greeter_item_size_request (greeter_geometry.c:387)
==32442==    by 0x80555A4: greeter_item_size_request (greeter_geometry.c:387)
==32442==    by 0x80555A4: greeter_item_size_request (greeter_geometry.c:387)
==32442==    by 0x80555A4: greeter_item_size_request (greeter_geometry.c:387)
==32442==    by 0x8055F27: greeter_size_allocate_fixed (greeter_geometry.c:146)
==32442==    by 0x8050311: main (greeter.c:1299)