The registration plugin is failing to send a notice that there is a registration pending about 10% of the time and I just had a reader who never received an activation email. I have contacted the developer for assistance in correcting the problem. I went through the entire user list this morning and found several others who were never activated. I have activated them and my sincere apologies to them for the late response.
If you register and do not get an activation email in 24 hr please contact the site.