These are programs that can hurt your computer (sometimes in surprising ways).
jacked is a problem on at least OS X 10.7 due to the way the Terminal application does 'Scrollback'. It appears to keep track of all output that occurs in the Terminal session in memory. If this output gets large, memory consumption will increase until the computer becomes slow. A few ways to avoid this:
-redirect large amounts of output to a file
-use "Command K" to clear the scrollback
-quit Terminal