Thank you, Cuyan, for bringing this to my attention:
We recently has a bunch of spam accounts initiated. They made it past the ReCAPTCHA verification, which suggests they are produced by sentient beings for the purpose of posting irrelevant advertisements to our forum. I will keep a closer eye on the newly-registered users list and make sure no such accounts get through the filters again.
If you are a newly-registered user, you are required to make your first post in the Welcome Forum before you can post anywhere else. This is a regrettable, but necessary security measure, in light of recent events.