for whatever reasons (Besides legal ones cuz thats a no-brainer).
for me:
a) penis pills - 1) i'ts bullshit that caters to insecure men who need to work on their self-esteem not their dick size. not to mention the ingredients have been found to be unhealthy in most of them.
b) same goes for other penis enlargers
c) pheremones. more bullshit. work on your fucking self-confidence and dating skills ala
http://fastseduction.com/
d) fake viagra shit that probably don't work. generic viagra is cool though. no problems with that.
im sure there are probably others but those are the main ones.
also those 3 make up 90% of the spam i see in email and newsgroups.
