With Gmail, j.s.m.i.t.h@gmail.com is the same address as jsmith@gmail.com as j.smith+nospam@gmail.com - it's likely that someone's mistyping their own email address all over the Internet (this happens to me all the time, having a common first name/last name combo. I get bills and newsletters and etc. Never got an underwear pic, though, alas!).

Good thing to remember this when writing a system that compares email addresses--always normalize Gmail addresses on the backend before processing--but woe betide you if you normalize on the frontend, people love their dots!