I therefore compared the users online between Thursday March 23 and Thursday June 1:

While the bottom of the curve is still about the same (3.5 million online at 0 h GMT), the peak of the curve has increased by 650.000 new users (6.5 million online at peak time, peak being around 15h GMT)!

Although this is only an average increase of 10000 new users online per day (at peak time) between those two dates, the average increase is now 14000 new users online per day in the last 2 weeks. So, in my opinion, yes, the North Americans are responsible for this acceleration.

And there is another point that makes me think this: the bottom of the curve has risen very slightly between the two dates, about 1.5%. But the top of the curve has risen by 11%! The top of the curve indeed is the time most Americans (North and South) are awake!

The next weeks will definitely be important to see if Skype continues to convince North-Americans to adopt their software. Last year, from the beginning of June till the end of August there was a clear slowdown of users online, see also my post here

Some days ago I had the feeling that we would reach 7 million concurrent users online somewhere in the third week of June. I however think that we will have to be patient and wait for September to reach that number. Because at the actual growth of 14000 daily new users online at peak time, we need some 30 days to cross the 7 million line, and I am almost sure by then Skype will experience the "Northern Hemisphere summer slowdown"!