Why am I getting all this spam?
Spammers (the people who send spam) "harvest" email addresses from various places. If you have done anything on the Internet at all (register a software product, participated in a online discussion board), your address could potentially be harvested by spammers.
Even if you hardly do anything on the Internet, as long as you have some kind of presence (even just an email address), your address could still be the target of spam messages. Spammers have been known to launch attacks similar to "cold calling"; they'll keep trying email addresses until they find a valid one. For example, a spammer could send a message to hawaii.edu addresses and just use all known common first names before the @ sign. The invalid ones will bounce, but the valid ones will get delivered.
ref: http://www.hawaii.edu/infotech/spam/spam.html#why
