More Skype context
A very highly valued reader and Skype-watcher has been tracking traffic figures intermittently (which I should have been doing all along - why don't I have a warehouse full of number-crunching slaves like I hear they have in the Bulge Bracket?), and has observed that average minutes of use per day on Skype appear to have trended above the 40m per day mark. My tally overnight confirms this, at 40.2m minutes. Staying in Eurocentric mode, let's look at this in the context of some recently-released market stats from France, one of the few markets in Europe where the regulator produces consistent and useful quarterly market data.
At 40m minutes per day, for what it's worth, Skype is currently generating a level of traffic comparable to 15% of the daily fixed line traffic for the entire French market in Q3 2004. Another way of looking at it is that Skype traffic is nearly equal to the combined outgoing fixed line minutes to mobile and international numbers from the French PSTN.
Based on these same stats, I work out that French fixed line channels (33.6m) and mobile users (42.3m) generated just under 13 minutes per day of combined outgoing voice traffic in Q3 (7.9 per day for fixed, 4.8 for mobile). Just how many Skype users there are in a given day, we don't know, but currently I see 1.7m users logged on. If we were to take a stab at an actual daily user figure of three times that level (this is based on a crude segmentation of a 24-hour day into the three big broadband population centers), it implies that the average Skype user generates 7.9 minutes per day of voice traffic - in other words, a level comparable to that of the average French PSTN user.
We can debate, and many are already, whether this usage is substitutional, incremental, or something else altogether. I suspect it is all three to some extent, but I don't know. Hell, what do you want for free?