David Recordon, one of the originating developers of OpenID, noted in his blog that social bookmarking service ma.gnolia has posted some initial statistics on new user adoption of OpenID.

Per the ma.gnolia newsletter, since the ability to log in via OpenID was enabled, 15% of all new users use OpenID as their primary method of logging in.

Now, for the initial release of a new technology that in all honesty behaves differently than standard single sign-on schemas, this is promising (with OpenID, you enter your OpenID URL at the consumer website, are redirected to your OpenID provider for logging in and are then sent back to the website - this is different from other SSO schemas which require login and password to be provided to the consumer website, or schemas such as Passport where you provide no information to the consumer website and then are redirected to a central login site).

Though 15% usage is admirable, the interesting thing would be to check the enrollment levels by day. I suspect that what happened is that when ma.gnolia's support of OpenID was publicised on the OpenID mailing lists, there was a flood of new registrations as OpenID enthusiasts logged in to test how it worked. The interesting process will be to determine if these users are still active/more active than normal users and after throwing out the enrollments from any initial week surge, what the real OpenID usage rate is.