A stupid example to poke at it, and fixed up some edge cases.

lib/stream.js

@@ -12,13 +12,13 @@ function Stream () {
   };
   this.resume = function () {
     buffer.paused = false;
-    flow(this, buffer);
+    if (!buffer.flowing && !buffer.paused) flow(this, buffer);
   };
   this.write = function (data) {
     if (buffer.closed) throw new Error("Cannot write after EOF.");
     if (data === null) buffer.closed = true;
     buffer.push(data);
-    flow(this, buffer);
+    if (!buffer.flowing && !buffer.paused) flow(this, buffer);
   };
   this.close = function () {
     if (buffer.closed) return;
@@ -27,7 +27,6 @@ function Stream () {
 };
 
 function flow (emitter, buffer) {
-  if (buffer.flowing || buffer.paused) return;
   buffer.flowing = true;
   if (buffer.length === 0) {
     buffer.flowing = false;

test/test.js

@@ -0,0 +1,51 @@
+var Stream = require("../lib/stream"),
+  assert = require("assert"),
+  sys = require("sys");
+
+// s1 | s2 | s3
+
+var s1 = new Stream(),
+  s2 = new Stream(),
+  s3 = new Stream(),
+  out = "";
+s1.addListener("data", function (chunk) { s2.write(chunk) });
+s2.addListener("data", function (chunk) { s3.write(chunk) });
+s3.addListener("data", function (chunk) { chunk && (out += chunk + " ") });
+
+s2.addListener("drain", function () { out += "\n--DRAIN--\n" });
+
+function message () {
+  out += "-1-";
+  s1.write("order");
+  s2.pause();
+  process.nextTick(function () { out += "-A-" });
+  setTimeout(function () { out += "-!-" });
+  out += "-2-";
+  s1.write("is");
+  process.nextTick(function () { out += "-B-" });
+  setTimeout(function () { out += "-@-" });
+  out += "-3-";
+  s1.write("guaranteed");
+  out += "-4-";
+  process.nextTick(function () { out += "-C-" });
+  setTimeout(function () { out += "-#-" });
+  s1.write("but");
+  out += "-5-";
+  process.nextTick(function () { out += "-D-" });
+  setTimeout(function () { out += "-$-" });
+  s1.write("NOT");
+  out += "-6-";
+  s1.write("synchronicity\n");
+  process.nextTick(function () { out += "-E-" });
+  setTimeout(function () { out += "-%-" });
+}
+message();
+setTimeout(message);
+setTimeout(function () { s1.close() }, 100);
+
+setTimeout(function () { s2.resume() }, 500);
+
+
+
+setTimeout(function () { sys.error(out) }, 1000);
+