Computer Security Scams
NEVER “test” your security or other system configurations by clicking a pop-up or other web ad.  It can fool you into thinking you are vulnerable when you are not by displaying your system information and telling you anyone can see it (even though only YOU can see it). 

Nigerian Scams
By email, a foreigner asks for your help to receive a bunch of money or assets, and slowly wins your trust so that you pay more and more money (sometimes even to a fake bank) to complete the transaction.  Some people even go overseas to complete the deal, end up robbed blind at best, and at worst are never heard from again.  This is no joke.

Getting even?  As long as you don’t give out any identifying information (bank number, fax number, etc.), string them along as long as you can.  They rarely understand English well, and don’t even have time to translate all the suckers’ emails in detail.  Remember, the more time they spend with you, the less time they have for someone’s grandma.

Get Listed on 1,000 Search Engines
Here’s some news — they AREN’T that many search engines.  There are only a handful of general search engines in English, and a few big directories of general interest.  The rest are specialized (and will not list you) or are email-address-collecting link lists that move you down (and off) the list as more people pay money to “get listed”.  Then they sell your email address.

Don’t ever use such a service, or you may have wasted your money (as many REAL search engines block automatic submissions anyway), and may even end up in Spam Hell.