[OpenID] Active user stats?

[Tara Kelly]

Hello all.
I'm new to the list, so I'll introduce myself: I'm Tara and I run an 
online password manager (PassPack).

We intend on accepting OpenID login in lieu of user/pass to enter the 
system. We've got a two-step login, so we can do this without 
compromising the data. What I'd like to figure out is how big the 
current user base is, and at what rate it's growing.

I've heard of "over 100 million OpenID identities created", but I also 
know that a large portion of those were assigned by AOL, Wordpress, etc. 
I'm looking for stats on voluntary/active OpenID owners. Any ideas on 
how I could go about getting such an estimate?

I was just over at JanRain and left a comment to this effect, but then 
thought I'd be better off asking here.
http://janrain.com/blog/2007/08/23/openid-ecosystem-continues-to-grow/#comment-362

Thanks for your help.
Cheers,
Tara