5. What are some common internet scams? Example: click scams, international modem dialing, paypal fraud, pump-nd-dump stock fraud, advance fee fraud. Nigerian 419, Spanish Prisoner, craigslist pay first scam. How do these scams work? How does the internet/web make this kind of fraud easier to perpetrate?

Here is some preliminary research I've done and the sources:

http://www.hoax-slayer.com/nigerian-scams.html#nigerian-scams
The "Nigerian 419" scam is titled this because 419 is the section of the Nigerian criminal code that the scam violates. The scammer claims in an email, craigslist ad, etc., that they need help accessing a large sum of money and they will allow you to keep a percentage of money in exchange for your assistance. Once you agree to help, you are charged fees (for taxes, etc.) and the main goal is gained access to your bank account.

http://www.consumerfraudreporting.org/CraigsList_scams.php
It is becoming increasingly popular on CraigsList for buyers to offer to sent money orders for more money than you're asking, and request that the remainder be sent back via Western Union. The money order will be bad, and they will have your money for good. This website gives a list of clues, one of the most important being "strange" English, most likely written by a Nigerian.

From personal experience, one of my friends signed up to be a "personal assistant" (she found the job on Craigslist) and her first job was to help this "artist" access a large sum of money. To do this, they first sent her a check to deposit in her own bank account, and then she was to take out some of that money to pay a fee. Luckily, she thought something was weird and quit in time. Another friend tried to buy a puppy off of Craigslist and encountered the second type of fraud listed above.

http://thespamdiaries.blogspot.com/2009/06/spanish-prisoner-scan-on-rise.html
The Spanish Prisoner Scam: Someone writes to you claiming to be a wealthy man stuck in a Spanish prison. He asks for bail and promises to pay you back (and then some) once he's out of prison. Secrecy is emphasized, and he usually says he cannot give his name because he's under the prison system with an alias.

http://darkreading.com/blog/archives/2009/06/facebook_419_im.html;jsessionid=3FSX1Z1DG5ICTQE1GHRSKH4ATMY32JVN
Here's a facebook scam about being held at gunpoint in London and needing money for a flight to get out.