The Disease is Rampant Stupidity, The Cure? Simple
I'm not quite sure why spam persists. If nobody bought anything from spam then it would cease to exist by the simple and immutable laws of economics, if a project becomes financially inviable then it fails and no one does that anymore. Why are the scams that get people to enter in their credit card information, social security number and everything else the fledgling ID thief needs to get started successful? Because they need a tiny, tiny percentage of "hits" to profit. One out of a million or ten million that responds with credit cards, bank account numbers, home phone numbers and social security numbers like trained monkeys. Just one person can ruin it for everyone by letting the numbnuts know that it will work, that people will give you all the information you need to assume their identity.

What possible train of logic is permitting people to fill in their information into an email? Why on earth are these people able to get through the rest of their lives relatively unvictimized?

How do people actually fall for these scams?

Here, allow Intellectual Poison to help out. Here's a short checklist for you to use if you suspect something is wrong with an email you just got from support@ebay.com or something like it.

a. Do they ask for information that you have to use a password to change on their site?
If yes then its a scam and should be reported ASAP.
If no then continue on.
b. Do they tell you that your account is going to be closed unless you give them this information?
If yes then its a scam and these people are trying to invoke a fear of loss response to get you to give them your credit and personal information.
If no then continue on.
c. Are there numerous misspellings, grammatical errors and other flaws that might indicate that the writer had a less than college level knowledge of English?
If yes then its a scam and they figure you are too stupid to know the difference between meet and meat.
If no then continue on.
d. Is it from a company you've never heard of and/or have never done business with?
If yes then its a badly targeted scam and should be reported and deleted.
If no then you should be able to verify the validity of the email by calling them up or replying (WITHOUT YOUR CREDIT DATA IN IT, SPEEDO). Note, I don't mean replying to the email itself which is almost certainly spam, I mean to get in touch with the company being referenced in the scam spam.

How hard is it to figure out that someone's trying to weasel your personal information out of you? Not very if all accounts are to be believed. Identity theft is one of the fastest forms of crime on the internet and it makes sense really. Assuming another identity is pretty easy and is a regular part of the internet experience. Only thing is that these people are doing it offline and making alot of money by scaring, cajoling or threatening people out of their personal information.

There are ways to combat ID Theft, hire a company to monitor your credit balances and changes. Shred your reciepts before trashing them. Don't fall for obvious garbage emails that purport to be from a company you've done business with and keep an eye on that little lock in the bottom corner of your browser (or where ever it is in IE) that tells you when you're dealing with a secure page. Never, ever, ever give away any credit card information in an email. Its far too easy to steal and people have sniffers out there searching for sequences of numbers they can rip and use.

The other thing to do is think about what you're doing and not give away info to strangers you can't say when you wouldn't give away that info to someone you met on the street.

It ain't that hard folks. Think before punching in your numbers. Make sure your cards have fraud protection built into them and don't allow yourself to be easily victimized.