An unkind word can get you a lot farther than you think. That's the latest takeaway from spammers who have learned that nasty messages with a personalized twist tend to deliver better clickthrough rates than offers of money or love.

"Using insults in the subject is a more targeted way to get the recipient curious or angry enough to open the mail and click on the link," Paul Wood, a senior analyst at anti-spam firm MessageLabs told The New York Times. "It makes the mail personal, because it is a direct insult using the recipient’s name."

One common ploy that seems to be sweeping the internet is spam that insults a recipient by telling him that he has a "stupid face." That campaign often leads to a malware site designed to rope the user's computer into a botnet scheme.

But beyond the nefarious details of this latest spam scourge, the change of tactics highlights the ongoing cat and mouse game that all commercial emailers -- legitimate and otherwise -- play with users who continue to develop ways to filter out unwanted emails.

According to a recent series on NPR's "Morning Edition," email could be at risk of killing itself because of email overload. The Radicati Group, a market research firm, estimates that 210 billion emails are sent each day. That's about 35 emails per day for each person on the planet. But when you consider the fact that many people don't have email or even internet access, the actual number is probably a lot higher.  

The sheer volume of emails and how users have responded to the overload, has put pressure on email marketers, who struggle to comply with an evolving legal regime while still trying to deliver individualized messaging from major brands.

As for the initial success of offensive emails, that development could prove to be a harbinger of an increasingly high bar for access to users' inboxes.