An analysis of nukeSPAM™ data after a significant increase in blocked registrations on another site yielded some interesting results:
Free and throwaway email accounts continue to top the list of spammers (and the site's blocked domain list has been significantly increased)
Spammers continue to spoof IP addresses (no surprise)
Gmail spammers insert random periods in the user name to enable one account to be used even after the primary email address is blocked
The screenshot of actual nukeSPAM™ data below shows the last 2 points (non-Gmail accounts - the first point - was filtered to highlight these points). Read more for some ideas on how to prevent this with modifications to nukeSPAM™ and to RNYA.