Don't think a VPN is right for you? Consider the following practical reasons to use a VPN service provider:
1. Securing Wireless Connections / Public Wi-Fi
If you use wireless hotspots / public wi-fi, your traffic is open to be easily monitored by both the persons providing the wireless access, and others on the wireless network (as they all have the security key). This makes session hijacking rather easy - as the recent FireSheep extension for Firefox demonstrates. In other words, it's quite simple for another person to hijack your Facebook, Twitter, possibly even your email account.
An attacker sitting in a coffee shop or on hotel wireless could gather dozens of accounts in short order using this method. By using a VPN, even on a wireless connection employing no security measures, you will prevent these types of attacks.
2. Hiding your IP address / Privacy
3. Viewing content outside your geographical area / bypassing censorship
Most VPN providers have servers in many countries, which will allow you to view content from websites that restrict access based on geographical location (e.g. Hulu, Comedy Central, BBC, etc.).
4. Preventing passive traffic monitoring
All traffic passing from your computer to the Internet is easily monitored and logged by an ISP. Many ISPs bury the fact that they do this deep in their Terms of Service when you sign up. If you use a VPN, all traffic on your connection will be encrypted from your computer to the VPN provider, and then pass to the Internet.
5. Preventing bandwidth throttling / traffic shaping
A LOT of ISPs engage in traffic shaping/throttling of certain types of traffic - BitTorrent traffic in particular. If you don't like the idea of your traffic being monitored and shaped, a VPN will prevent this by creating an encrypted tunnel between your computer and the VPN provider. The ISP can only see the tunnel - but not the ports being used and the traffic protocols passing through the tunnel.