Spam: An Escalating Attack of the Clones in the New York Times:
Spammers are like fruit flies. They multiply. They are elusive. Worst of all, they evolve quickly. The most aggressive spammers have become very sophisticated, constantly varying subject lines, “from” addresses and body text.
Brightmail says the volume of spam it encounters has almost tripled in the last nine months. The company adds that 12 to 15 percent of total e-mail traffic is spam; a year ago, that figure was closer to 7 percent. Brightmail, which maintains a network of In boxes to attract spam, now records 140,000 spam attacks a day, each potentially involving thousands of messages, if not millions.
Spam is the biggest problem with email. NYT also has an article on tips to combat spam.