Well, if this script is being called only once, such as with a cron job, that's fine. However, if you were to put this into a CGI script, the number of processes or memory could quickly get out of control. You could add a check to see how many processes are running under the user. Then you could kill it (or something else that's cleaner) if there are too many processes, or too much memory is used. This might be the best of both worlds.