After all, you can simply bookmark and come back to an unlocked journal if you want to 'check out' that person more before you decide to add them, whereas often that sort of information isn't as available on locked journals.
ETA: While I'm not much of a 'friender' (being utterly rubbish at appraoching people), locked journals seem to put me off even more, no matter how interesting the person seems. Which probably says more about my state of mind than anything else.
I should remember to take my cd player to college with me. It stops all these random thoughts.