Hi Harry,
Good points. I totally disabled cookies when I got my new email address and I have yet to recieve one junk/spam email (knock on wood). The only times I turn them on is when I need them for an important site that requires them (online shopping, etc.) Just take a look at the kind of info. banner ads like DoubleClick can get with their cookies:
http://users.rcn.com/rms2000/privacy/banads.htm