Awkward questions for you. Have you ever had your Facebook, Twitter or MySpace accounts hacked? How did that happen. Did they guess your password? Now consider if only one of your accounts has been hacked. Are you using the same password on other sites? How long will it be before the others are hacked too? How will you know? What if you use the same password on your bank account? Doesn't bear thinking about, does it?
So what password have you used? Is it easy to guess? Surprise yourself. Enter "Common passwords" into Google (click on the link - it's there for you) and see if you've ever used a password that is in the top 500. Apparently 1 in 9 of you will use a password from this list. So there is a good chance that out of pure luck, a hacker will be able to hack your account on these social network sites in minutes then they can pretend to be you, or they can misbehave as if they were you, or worse, they can steal your information.
Now imagine when entire systems are compromised as happened recently to lifehacker. This was reported by a number of news sites including the BBC and has prompted a lot of warnings asking you all to change your passwords on your favourite sites and to make sure they're strong enough. So how should you choose a strong password? More importantly, how do you remember it? A good password to use then is one that is hard for others to guess (therefore it is strong) yet easy for you to remember. There are a number of guides on the Internet you can find to suggest ways of choosing a good password, but a simple one you can use is to choose a line from your favourite song, or a quote from a film. Now take the first letter of each word from the line, replace some letters with numbers (eg: replace I with 1, o with 0, e with 3 etc.) and you can easily generate a good password. For example, a hacker or cracker would have trouble guessing ia8g1m8W if that was your password but you would remember it if you'd chosen "I'm a Barbie girl, in my Barbie world". You could also make it stronger still by adding punctuation at the end as I have in this second example N1tW0od! This is the opening line from Shakespears' Richard The Third - "Now is the Winter of our discontent".
Obviously you shouldn't use these passwords, but you should now have enough to go try it for yourself and see. Check how strong your current password is using the Password Meter. Then check again after you've used the above technique.