Related, reminds me of the havoc you could wreck on phpBB boards with [you] command enabled. For those who haven't seen it, a [you] BBcode is replaced on display with viewing user's name.
So you'd generally write a reasonably sounding comment, with a sentence like "This is something [you] was supposed to do.", you'd post it and then it was time to eat popcorn.
Memorizing and reusing a single password is the worst thing you can do. The number of leaks and brute-force attacks are increasing, and you should really be generating random and unique passwords per website if you aren't.
To get an idea of how easy it is to crack a leaked password, download a public list of a website you know[1] (ex. L1nk3d1n), you'll probably find the password you used at the time of their leak in the list, since ~97% of them have already been cracked.