I liked RK's post on the Facebook phenomenon, especially the idea that as these networks get more advanced they have a greater chance of 'condens[ing] meaning from the vapour of nuance.' Unfortunately, other things are getting condensed in the meantime, from the extreme of stranger danger to the annoyance of unwanted friendship requests. I've been looking for technical ways to mitigate the harm and thought I'd share the wealth.
For the stranger danger, check out the 'Privacy' page - set up who can see your profile, photos, video etc. It is crazy that this is not a step by step process when you create a profile, but the controls are pretty good.
The unwanted friends are a more difficult problem. Facebook seems to require that you draw a line through the swirling grey motes of social interaction and definitively state who is a friend and who is not. One option is to say no to people who are borderline to preserve the integrity of your list but that can have repercussions in the real world. Another way is to be generally permissive, but screen out the social detritus so they don't pop up in your news feed.
To find this hidden feature, click 'help' in the lower right corner, then 'How does the news feed choose stories' then 'News Feed Preferences'. Then enter the names of people you don't care about in the lower right box.
This is not the slap in the face of rejection or limited profile status, but does remove them from your radar. They will still be able to post on walls, see photos etc, so it's only recommended for people you don't care about, not toxic weirdos.