export - Why does this simple program leak memory?

I have a simple Mathematica program which writes some plots to image files for later conversion into a movie. Unfortunately, the program leaks so much memory that it quickly exhausts all 12G of RAM on my machine. The only way out is to quit the kernel(s).

I can't see why this program shouldn't use a bounded amount of memory. I've read through Debugging memory leaks which unfortunately hasn't helped - the only "heavy" symbol is 'data', whose size is fixed. I don't see what's growing!

Note that the same problem occurs regardless of whether the loop is Map or Do, Parallel- or not. The problem also occurs in both Mathematica 8 and 9, both under Linux.

Help?

(* number of frames *)
n = 1000;

(* just some bogus data *)
makeData[_] := Table[{{x, y} = RandomReal[{-3, 3}, {2}], {y, -x}}, {200}];
data = Array[makeData, n];
(* Export the frames *)
ParallelMap[
  Export[
    "movie-" <> IntegerString[#, 10, 4] <> ".png",
    ListVectorPlot[data[[#]]]] &,
  Range[1, n]];

Edit:
Some more information: after running this code (the non-parallel version), I checked the memory usage of the processes involved. The percentages are out of 12GB, so both the frontend and the kernel are consuming quite a bit of memory, while PNG.exe is almost nonexistent.

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
24575 gredner   20   0  4400  740  588 S    0  0.0   0:00.00 Mathematica        
24646 gredner   20   0 3029m 2.3g  22m S    0 20.5   1:43.02 Mathematica        
24655 gredner   20   0 3384m 1.6g  14m S    0 13.7   3:31.47 MathKernel         
24984 gredner   20   0  387m 7364 2464 S    0  0.1   0:20.92 PNG.exe