I'm the editor who worked the Thomas Powell on this article and I am posting his response here.

"Much of the conventional wisdom about Ajax is simply wrong.

Take a look at this demo, I outline in my book about Ajax: http://ajaxref.com/ch6/requestqueue.html

It shows the following:

Ten requests are spawned all asynchronously. The first will have a five second delay, the second will have a seven second delay and the rest will have no latency.

In this example, I have the library timeout around 5 seconds, and thus, given a two connection limit with the two slow pokes in the front, everyone timeouts. If you click on request queue, which will order the requests, you will see that just the first two timeout and then everybody else goes through.

That looks like a limit to me. -- TAP"