Multiple attempts to register using the same I.P.

I have today banned 3,or 4 different user names all using the same I.P. 69.23.242.216 (tammy@yeastinfectionsymptoms.com ) This info from www.stopforumspam.com/ipcheck which shows this I.P. having a spam history. Does this happen often, or is it just a determined spammer.