Spam is like superglue; once you get it on you, it is difficult to get off. We want to do our part to fight spam abuse by raising awareness in visitors to our site. For things you can do to protect yourself from spam, see the tips on spam.abuse.net or Clueless Mailers and for a legislative slant, see the Coalition Against Unsolicited Email.
For web page creators, a simple technique is to obfuscate any email addresses appearing on your web pages. This technique makes your email address appear normally to visitors to your web page (just as we've done here on CleanCode) but prevents address-seeking robots from getting your email address. A great discussion of techniques to do this is presented by Keith Bell here.