I don't bother reporting spam on one account. In fact, I created a rule specifically filtering spam to go to my inbox. Pretty much the only people who bother me are those who don't set their dates properly. What I mean is they set their spam to say June 02 on an email sent on February 06 of the same year. I will not hesitate to report any such email as spam. This doesn't happen often but I hope google (or any email provider) punishes such senders severely maybe even blacklist the domain.