I noticed that last night the concurrent users online went below 4 million. Quite normal "night dip" for a Saturday to Sunday night, but hasn't been that low since a long time. This is also an indication that we are entering a summer slowdown, see my explanation on this phenomenon in my post of September last year.
Skype growth is however clearly slowing down!

We will not reach 10 million concurrent users online before September (my guess), and then it will have been more than 200 days to acquire one additional million. The only time it lasted longer was for the acquisition of the first million concurrent users online: it took 418 days!

In 2006, Skype grew with 3.84 million concurrent users online (at peak time). Now in the first 6 months of 2007 we only have added 1.22 million users (see the table below)!

So what? Has Skype really reached some "saturation level"?

Jean Mercier analyzes the trends on his Skype Numerology blog.