You might do it to gain access to features or functionality that your gadget/service provider should offer but doesn't. Or maybe you just want to avoid something you prefer not to do--like coughing up your e-mail address just to gain access to a site's content, or (ahem) paying for stuff you'd rather get for free.
And sometimes you do it because, well, it's awesome.
But awesomeness has a price, and every activity described below carries a risk. Potential fallout ranges from violating terms of service or voiding a warranty, to bricking your favorite gadgets or having a clutch of copyright attorneys descend upon you from a great height.
So these are things you really shouldn't do. Really. And if you tell anyone where you heard about them, we'll deny everything.
1. Jailbreak Your iPhone
Apple iPhone owners fall neatly into two groups. Members of the first group suffer under the yoke of tyranny, endure arbitrary rules over what they can and can't do, and put up with crappy reception (be careful how you hold that thing).
Members of the other group have jailbroken their phones, hacking iOS whatever to get to features, apps, and carriers that are otherwise verboten. There are many ways to unlock the uber phone, but by far the easiest is with Jailbreakme. Simply visit the site jailbreakme.com from your iPhone's Safari browser, and you're done. It also works on the iPod Touch and the iPad--but only if your hardware uses iOS 4.01 or an earlier operating system.
Why this is awesome: Let us count the ways: (1) No more AT&T. You may be able to use your iPhone with other GSM-based telecoms such as T-Mobile. (2) No restrictions on the apps you can use. The Cydia store features dozens of apps that work exclusively on jailbroken iPhones. (3) Have we mentioned no more AT&T?
Why you shouldn't do it: It's a constant game of cat and mouse between Apple and the jailbreakers, and Apple is the cat. Eventually the cat will win and your jailbreak will fail, possibly leaving you with a pretty paperweight (and no warranty). Also, you'll make Steve Jobs sad.
2. Let Pandora Out of Her Box
My personal history is divided into two parts: BP (Before Pandora) and AP (After Pandora). That's how much this streaming music service has changed my life. Unlike normal radio, it plays songs I've never heard before yet instantly love.
Why this is awesome: Great music for free.
Why you shouldn't do it: Pandora's terms of service forbid copying, storing, altering, or otherwise stealing the music tracks it streams. Also, if you do anything that ends up getting Pandora shut down, I will personally come to your house and pummel you. And I'll bring Chuck Norris.
3. Maintain Multiple Facebook Identities
A Fakebook persona is good for more than just stalking your ex or posting nasty things about your boss; you can use it to say or "like" things without repercussions, or play FarmVille and other obnoxious Facebook apps without risking your personal information and annoying your real friends. All you really need is an e-mail address, a pretty picture, and some bogus details--and you're off to the races.
Another benefit: You can do what my son did and create a second G-rated Facebook account to deceive your parents and other adult relatives while saving the real one for your peeps. (Kids, if you do try this at home, remember: Don't log into the real account from dad's computer and then forget to log out. That will not go so well for you.)
Why this is awesome: No privacy risk and very little chance that your employer or loved ones will know it's you (unless, of course, you log in and forget to log out).
Why you shouldn't do it: It violates Facebook's terms of service, which means real you and fake you could both get the boot. Of course, Facebook often fails to follow its own rules, so why should you treat them as sacrosanct?
4. Get Creative With Wikipedia
Why this is awesome: You can practically hear that Wikepedian's sphincter tighten as you engage in an edit war over Lady Gaga's man parts. (But seriously, has anyone ever seen Lady G. and Zach G. in the same room at the same time?)
Why you shouldn't do it: You could be banned from editing any more entries. Also, an entire generation of 5th graders may grow up thinking that the capital of Arkansas is Bozoville.