That kind of registering using capture ('captua' not just signing in) should stop bots from registering and spamming, but will do nothing to stop drive by spamming that is generally the issue human registering and posting a few posts.
The current forum registration is a two step process 1) register for membership including an email address, 2) you are then sent an email with the final step, an activation code.
This ensures a real email has to be given so the second step can be received allowing activation. I know this isn't much to use a throwaway email, but that has to be better than a single step process and effectively blocks bots, but not a determined drive by spammer, that requires users to report all spam.
Yes, the internet is in some cases getting more difficult to access, but having to register at a site just to access the information and not to post is crazy how many forums would you have to register at if they all implemented this practice,