1.. The free ride.
E-mail spam is unique in that the receiver pays so much more for it than the sender does. For example, AOL has said that they were receiving 1.8 million spams from Cyber Promotions per day until they got a court injunction to stop it. Assuming that it takes the typical AOL user only 10 seconds to identify and discard a message, that's still 5,000 hours per day of connect time per day spent discarding their spam, just on AOL. By contrast, the spammer probably has a T1 line that costs him about $100/day. No other kind of advertising costs the advertiser so little, and the recipient so much. The closest analogy I can think of would be auto-dialing junk phone calls to cellular users; you can imagine how favorably that might be received.

2.. The ``oceans of spam'' problem.
Many spam messages say ``please send a REMOVE message to get off our list.'' Even disregarding the question of why you should have to do anything to get off a list you never asked to join, this becomes completely impossible if the volume grows. At the moment, most of us only get a few spams per day. But imagine if only 1/10 of 1 % of the users on the Internet decided to send out spam at a moderate rate of 100,000 per day, a rate easily achievable with a dial-up account and a PC. Then everyone would be receiving 100 spams every day. If 1% of users were spamming at that rate, we'd all be getting 1,000 spams per day. Is it reasonable to ask people to send out 100 ``remove'' messages per day? Hardly. If spam grows, it will crowd our mailboxes to the point that they're not useful for real mail. Users on AOL, which has a lot of trouble with internal spammers, report that they're already nearing this point.

3.. The theft of resources.
An increasing number of spammers, such as Quantum Communications, send most or all of their mail via innocent intermediate systems, to avoid blocks that many systems have placed against mail coming directly from the spammers' systems. (Due to a historical quirk, most mail systems on the Internet will deliver mail to anyone, not just their own users.) This fills the intermediate systems' networks and disks with unwanted spam messages, takes up their managers' time dealing with all the undeliverable spam messages, and subjects them to complaints from recipients who conclude that since the intermediate system delivered the mail, they must be in league with the spammers. Many other spammers use ``hit and run'' spamming in which they get a trial dial-up account at an Internet provider for a few days, send tens of thousands of messages, then abandon the account (unless the provider notices what they're doing and cancels it first), leaving the unsuspecting provider to clean up the mess. Many spammers have done this tens or dozens of times, forcing the providers to waste staff time both on the cleanup and on monitoring their trial accounts for abuse.

4.. It's all garbage.
The spam messages I've seen have almost without exception advertised stuff that's worthless, deceptive, and partly or entirely fraudulent. (I include the many MLMs in here, even though the MLM-ers rarely understand why there's no such thing as a good MLM.) It's spam software, funky miracle cures, off-brand computer parts, vaguely described get rich quick schemes, dial-a-porn, and so on downhill from there. It's all stuff that's too cruddy to be worth advertising in any medium where they'd actually have to pay the cost of the ads. Also, since the cost of spamming is so low, there's no point in targeting your ads, when for the same low price you can send the ads to everyone, increasing the noise level the rest of us have to deal with.

5.. They're crooks. Spam software invariably comes with a list of names falsely claimed to be of people who've said they want to receive ads, but actually consisting of unwilling victims culled at random from usenet or mailing lists. Spam software often promises to run on a provider's system in a way designed to be hard for the provider to detect so they can't tell what the spammer is doing. Spams invariably say they'll remove names on request, but they almost never do. Indeed, people report that when they send a test ``remove'' request from a newly created account,, the usually start to receive spam at that address. Spammers know that people don't want to hear from them, and generally put fake return addresses on their messages so that they don't have to bear the cost of receiving responses from people to whom they've send messages. Whenever possible, they use the ``disposable'' trial ISP accounts mentioned above so the ISP bears the cost of cleaning up after them. I could go on, but you get the idea. It's hard to think of another line of business where the general ethical level is so low.

6.. It might be illegal.
Some kinds of spam are illegal in some countries on the Internet. Especially with pornography, mere possession of such material can be enough to put the recipient in jail. In the United States, child pornography is highly illegal and we've already seen spammed child porn offers. Any one of these six would be enough to make me pretty unhappy about getting junk e-mail. Put them together and it's intolerable.