I've begin to see alot of my friend's comments on THEIR friends walls and posts in my news feed. I'm not sure if that is what they want (perhaps, it is, and I don't really mind) but I do wonder if they realize the extent to which they are sharing (and sometimes, oversharing). One of the best ways to find out what you share to facebook is to have a friend help you out. You can then return the favor with them. Of course, the friend doesn't have to be a 'real' friend either. ;-)
So, since I just got accidentally ( I think) invited to a wedding shower, here is how to control what displays:
Under Account > Privacy Settings > Things Others Share (i.e., what your friends can post from your account) Can see Wall posts > Choose wisely.
Really, you should read this section very carefully -- this is what others can post about you. I have Can see Wall posts under Things Others Share as set only to me. You can still see the ACTIVITY (FB doesn't give you control over who sees the ACTIVITY (e.g., likes, comments, etc.) but you can control who sees the actual CONTENT (e.g., the message)