I've noticed recently that there has been an increase in 'spam-like' registrations on the website, where the email address looks 'phoney', usually appearing to be a sales or admin address from a company. To avoid too many such accounts clogging up the system, I have implemented a basic 'captcha' system on the registration page. All the user has to do is count how many objects are in the picture and enter the number in the box. Hopefully this should reduce the number of 'spambots' registering without preventing anyone from taking part.
 
Unfortunately at the moment, this doesn't work with things like screen readers or other accessibility software but hopefully this will change in the future.