NCR: Email spam question

I used to get just a few spam emails every now and again. Latley ive been getting about 20 a day. I send em to my spam folder and i somtimes get the same ones again. I guess they change the email address a bit? Anyway, i havent signed up on any web sites with my email or anything so i was woundering why im getting so many more? Is anyone else getting increased spam emails as of late?