I haven't posted here in a while, but I'll make an effort to do so. It is valuable for me to have some thoughts and references stored somewhere for easy, ubiquitous access.
It turns out I accepted to serve on the Globecom PC this year, and I just noticed that they will open a rebuttal phase for the authors. This is very intriguing: globecom receives relatively short papers, usually not very mature work. Someone once described the publication phases in networking as: workshop paper -> globecom or ICC -> infocom -> journal, as the results mature and become more complete. Also, Globecom is not very selective (say, 35-40% acceptance rate nowadays).
On the reviewer side, I can only speak for myself, but different conferences call for different level of scrutiny and time spent reading the papers. I see my job for Globecom as sorting the papers out, not as much as providing feedback to the authors: since the work is still in progress, I give a general indication of whether I think it's worth pursuing. But I won't go into the details of a still immature, evolving research. Mostly, unlike a journal or an Infocom/Mobihoc/MobiCom review, I keep it succinct. I usually keep my notes after a review, but I might not go through the trouble with 2nd tier conferences. Had I known there would be a rebuttal, I would have, dang.
As an author, I have wished in the past there would be a rebuttal. As a program chair, I've had (unrequited) rebuttal emails from disgruntled authors (who had a point, I'll concede that a clarification was necessary). So authors like rebuttals, solicited or not. That and my short reviews, it might be an explosive mix!