As a guy who travels around a lot, I know the value of being able to change my IP address. You'd be surprised how much information can be attached to your IP, and what you can or can't get done with certain IP addresses.

For example, when I use the wifi at my local cafe, I use a VPN to access the Internet. With a VPN I can secure the IP address of my computer while sharing an Internet connection with people in the same cafe. Call me a conspiracy theorist, call me paranoid, but I've heard and read a lot about how people can steal your identity online. One of the most common ways to do this is by sharing an Internet connection - just like in a cafe or in a dorm. I'm not a hacker, so I don't get the inner-workings of it, but apparently its pretty easy to "jack" passwords and login information from people this way. So I change my IP with a VPN when I use the Internet on public wifi zones.

When I leave the US, my computer of course takes on the IP of whatever country I'm in. When I'm in Mexico, I get a Mexican IP. When I'm in Europe, I then get the IP of the European country I'm in. Sometimes, depending on the country, I get denied access from different sites. Certain article directories, membership sites, and other blogs or what not have a bit of a bias toward certain countries. It's not uncommon to get blocked or temporarily denied access to these sites based on IP. In this case, I also use a virtual private network to change my IP address to an American or UK IP. Hulu, Netflix, and BBC iPlayer can also be accessed in this way.

One of the worst situations is when I go to China or some countries in The Middle East / Africa that seriously censor the Internet. By blocking sites using a firewall, they can take out entire sets of IP addresses. Facebook, Youtube, Twitter, and a bunch of these other social networking or blogging sites have a bad rep with governments, and you need a VPN to unblock these sites. By changing my IP address with a virtual private network, I can get an IP outside of the country (some place like Holland, The UK, America, Canada, etc), and surf sites as if I was back home.

One of the more common reasons one might have to change the IP of his or her computer is of course to get past firewalls at work and school. Ok, it's not the most noble cause, but it's great when you boss blocks Facebook, but you've got a proxy under your sleeve. I usually use a web based proxy at work to change my IP address because I don't have to install anything on the computer. This means that I can use it on any computer in the office, and it leaves no traces!