Many offices and schools monitor email messages looking for things that are "inappropriate". If you share links with your friends, you may get in trouble if you are sharing links to pages that contain material that violates the usage agreements at your office or school.

One way around this problem is to hide your links by using an intermediate service. http://www.tinyurl.com is one such service, you give it a URL and it creates a new URL to the tinyurl.com domain which, when requested, then redirects to your original site. While this may fool some people, the people reading your mail can still go to the link and find out where it ends up at which point you are busted.

A new service called HideLinks is offering a similar type of URL-shortening service, but with a twist. They allow you to create a password for conversion. When the shortened URL is requested, it doesn't just redirect you to the target link, it requires the password first. If you and your friends agree on a common password, you can then use this service to hide your URLs and even if someone is reading your email, they won't be able to find out where the URL goes to.