excessive memory usage on large incoming http request?

gistfile1.js

// run this locally: node <gist.js>
// then POST a big (>300mb) file to it with cURL:
// curl -X POST -d @"/path/to/big.file" localhost:8080

var http = require('http')
var PORT = 8080
var peak = 0

// watch mem usage
setInterval(function () {
  peak = Math.max(peak, process.memoryUsage().rss)
  console.log('memory usage ' + (peak / 1000000).toFixed(2) + 'mb')
}, 500)

// http server
http.createServer(function (req, res) {
  
  // create a destination
  var dest = http.request({
    port: 8080,
    method: 'POST',
    hostname: 'remote.server.com'  // a running instance of https://gist.github.com/4449811
  }, function (resp) {
    resp.pipe(process.stdout)
  })
  
  dest.on('finish', function () {
    console.log('request ended')
    res.end('all done\n')
  })
  
  // pipe incoming data to dest
  req.pipe(dest)
  
}).listen(PORT, function () {
  console.log('server listening on ' + PORT)
})