Abusers have been thrown out by their providers, but the clever ones are setting up their own shops. For an advertiser, especially one that isn't concerned with the prospect of aggravating a few thousand users in the hope of generating a few hot leads, spamming can be almost ir-resistible. One simple message can be blasted out to thousands if not millions of e-mail accounts without the inconvenience and expense typically associated with design, printing, distribution, and postage. The drain on the network is overwhelming. The drain on the user is no less noteworthy given that users bear the cost of downloading time.
Many spams are the result of ignorance.
New users have something to sell or promote, and they see a list whose members share those interests. The users committing those acts are usually quickly made aware of their crime and shamed into changing their behavior. Other abusers are more sophisticated, and they rarely respond to shaming. In addition, the line that separates good and bad behavior in this regard is not always clear. Conference promotions, for example, frequently are distributed en masse via the Internet without raising the ire of users as long as the content is on topic.