I think one of the worst email scams going is phishing.  Not only does someone just send you a fake email that may or may not be true, but they try and trick you into thinking they they are a legitimate website.  Phishing is where you recieve and email with the look and feel of a real website, but it is from a scammer who wants you to click on it.  It could either place tracking cookies on your computer, or install a program when you click the hyperlink.  Usually they are in the form of "change your password to avoid a penalty" or "update your account info to stay active."  Some of them are incredibly detailed and look exactly like an authentic webpage - they will even use real links to the website so they "prove" that they are legitimate to thier reader. 

These are the worst because it can take a trained eye to catch a good phishing email.  Many people don't even notice the minute differences and willingly enter their personal information thinking it is legitimate. 

~Rex