if you know how to use Terminal, you can secure-erase your user data as well..
let's say your name is tom, and the new owner is Bill..
1. create a new user for the next owner..
go to sys pref's, amke a new Admin user - - - > "Bill"..
2. go to the root of the hard drive, and look at the name of YOUR user folder.. for instance if you're Tom Smith, it might be "tomsmith"
*BE WARNED.
BE VERY WARNED.
BE DOUBLE SURE YOU DO NOT NEED YOUR DATA BACK.
**YOU WILL
***__NOT__**GET YOUR DATA BACK IF YOU DO THIS
*!!!!
IF, and only if you are dead sure you do NOT want any of your user data left on the drive, then..........
quit sys prefs, to to terminal, log in as SU, and put in your root password..
then type in srm -fsRv /Users/tomsmith
(((substitute your username in this (instead of "tomsmith")....
press return
terminal will hard-erase the Users folder.. all of it.
it will be gone. byebyebyebye..
it will also take a while, depending on how much space your data used