For very-long-running requests, this isn't much different from making a purchase and waiting for it to appear at one's doorstep. Some UI is needed to view status so buyers don't order the same item twice. Similarly, for BI scenarios: Did I ask for that long-running report? I can't remember and I'd like to avoid burdening the system with duplicate requests if at all possible. Did my request fail becuse I was going through a tunnel? Inquiring minds want to know. Getting notified asynchronously usually isn't enough.