If you've never used Swiftkey, you should give it a try: it's a smart keyboard that uses some crazy-intelligent algorithms to predict what word you're going to type next. It's spooky. Whatever you do, don't lend your phone to a friend.
Because SwiftKey learns from what you've typed in the past — whether it be on Facebook, Twitter or in text messages — it's also been reading your confessions, tracking your romantic encounters and learning what gets you off. So when a friend starts typing something on your phone, well... they might be in for a surprise. [XKCD]