Do da research dey do?
I'm assuming a lot of members are checking things out but just aren't logged in, and a good amount of people are too shy, or lurking. Don't want to sign up until they have a better grasp of the hobby//interest, and have something to contribute or say, but Idk I could be wrong in my assumption. Plus, with the drive from WL's new online ad campaign more and more people are getting introduced to lasers everyday, and think they're cool, but don't want to pay over $400 for a 1+W laser. Just my thoughts though, again could be wrong, but I assume that counts for a good portion of those.
Looking at it again, there don't seem to be any more members registering than normal, so I am going to say it's bots. Out of all those guests you'd think some would sign up, even if only 1 in 100 of the ~40,000 did it would be a LOT for one day.