Second Life does no longer provide PCU numbers in their reports or xml.
This probably means that their numbers are declining. It is not so good news for MMOData.net. The latest number I got, 71k, derrived from Dwell on it, confirms that assumption. Furthermore Linden also stopped publishing monthly logins since october 2010.
Dwell on it seems still able to get the 14-day PCU numbers.
Either way, I will try to contact Linden Labs to see if I can get some more information.
On a brighter note, Perpetuum Online has contacted me to provide numbers, they are small, but it does not matter, and they use the same server strategy as EVE Online, so that may become interesting.