Andy is usually a great read but in this case I think that he has forgotten one of the most important parts about an IP-PBX and voice overhead - the ~ 80k load - is only applicable when someone is actually talking. Upwards of 50% of any phone conversation is actually silence - pay attention next time you're on the phone and see how much time there no one is actually talking...it may surprise you. There is actually so much silence in a typical phone call that Cisco had to artificially simulate "white noise" on their IP phone handsets so that people would stop saying “hello, are you there?”
Of course, there are a number of other problems with the call going out over the wilds of the internet not the least of which is the total lack of QoS - that's a bigger problem then the limited bandwidth of a DSL circuit...and last time I checked cable modems actually had a higher penetration....though that doesn't solve the bigger problems which is most people quote DOWNLOAD speeds and it's quite common to have a significantly slower UPLOAD speed. A 1 MB downstream circuit may have an upload speed a quarter of that.
Andy did have a good point in questioning the who/what/where/when/why of deploying this solution. I’m thinking that it will be more then the typical CDW customer will be able to handle on their own. If they have 1000 VAR’s already lined up I’m guessing that they are counting every POS that currently sells Linksys gear as a VAR and that’s a recipe for disaster! These people are used to handing over a low end switch/router – not a telephony product.
Interesting concept, I’m just not to sure how it’s going to play out.