One of the blogs I read is The Corporate Rat and The Elusive Cheese. Interesting name, but here's a blurb about the people involved.

CorporateRat (Arjun Roychowdhury) works for Hughes Systique Corporation, as Director of Broadband Application where he is responsible for driving technology focus and customer acquisition in the Broadband Application space.

ElusiveCheese (Sunil Veluvali) works for Sylantro Systems as Director of Engineering, where he is one of the key architects and is currently responsible for strategic initiatives.

This post delves into Skype and I really like the way these guys explain things. You might want to dig back through their archives as they've had some really insightful posts in the past 2-3 months.

SIP and Skype, P2P and Supernodes - what a melee
By CorporateRat

Gaaah. I happened to bump into Slashdot today and read this:
“…is that when you install the Skype client, it will drain system resources by running as a supernode from time to time” 
and finally concluding that the author will more likely use SIP over Skype.

Implictly implying that with SIP, you are free from such issues !

Let’s get the facts straight:

• P2P is an architecture, SIP is a protocol. Skype is a product, and Skype uses its own proprietary protocol (you can call it ‘Skype Protocol’ if you want).
• A SuperNode system forms a fundamental design choice of many existing P2P networks, including Skype, Kazaa, Grokster and several other massively scaled networks.
• Today, most of SIP’s deployment uses a centralized architecture. In other words, all your SIP phones register with some central server and some central proxy. Your calls are routed through them. If they fail, you cannot reach other users, or, will have to attempt to call them directly (not as simple, because the person who is sitting in your buddy list as sippal@myisp.com may actually be user457@001dxp.bbcppcspool.myisp.com and this complex ID is mapped to its simpler one by the proxy /location server that went down.
• There is current frantic work going on in the p2psip mailing list which is attempting to solve the following issues:
• How does one map a SIP flow over a P2P network ?
  
• Does it make sense to deploy a SIP overlay over a P2P network with common architectural principals of existing P2P networks (like DHT, for instance), or,
  

Does it make sense to deploy a P2P network over the SIP protocol ?