Recent Risks on Internet

1. URL shorten service.
Hidden of advertisements or even worse, malicious websites.
Lost of service if the URL shorten service provider is down or hacked.

2. Websites, especially SNS, request user to provide email login and password in order to add friends.
Do they really need your password to just get a list of your friends?
Even the websites requesting your credentials are trustworthy, you are still at risk. For example, some website can add your friends on MSN or Gtak by requesting your logins and passwords, but your credentials are transferred in plain HTML to them. This means sniffers can get your passwords with ease.
There is no reason to request your password while other methods like oauth are available.

File names you can NOT create on Windows

Try to create a file named NUL.txt on Windows XP, and you probably get an error message.

Many characters are not allowed for file names on Windows. This includes
< > : " / \ | ? *

Besides, many reserved device names should be avoided. This includes
NUL, CON, PRN, AUX, COM1, COM2, ..., LPT1, LPT2, ...

Also, using the device names unintended might raise security vulnerability.