What is the point of Jailbreaking an iPod Touch 4?

I have an iPod touch 4th generation and am debating on whether or not I should jailbreak it. Before I even figure out how to do it, what are the pros and cons of jailbreaking? I know you can get apps for free but I also know doing so voids warranty. Bottom line, what are the main negative outcomes that comes with Jailbreaking? A list of good and bad would be great. Best answer at my discretion much appreciated.