I know what you mean about the sharing Stellajane! I have friends who have posted every detail about relationship breakdowns or serious illnesses on their FB pages - even if you have it set to 'friends ony', there is always a risk someone could hack your account and gain access to it - and as most of them have over 1,000 'friends' listed anyway, they are already sharing with people they won't know that well. The other extreme is the people who share extreme trivia - "just enjoying a nice cup of tea and a sit down" or "I have a really bad headache". Oh, wow!
It does have it's good points though - I have a number of friends living abroad, some in areas where the postal service is quite erratic - in fact I have given up writing to one family as posted items hardly ever arrive! Facebook means I can stay in touch online and share photos which would never arrive if sent by post! I've also been able to get back in touch with a couple of very good friends - we all moved at the same time, so our new addresses never reached each other and now we are back in touch through FB. It's also good for linking people up with similar interests - I have linked up with a group of local volunteers who help homeless people. We are able to achieve much more working together, and I would never have known about the others if it wasn't for FB!
I just have the two rules - think about who I am sharing with before I post anything and also think 'if someone hacked my account and shared this round the world, how would I feel?' It's not just about avoiding bullying - the more you share online, the more at risk you are from identity fraud, theft etc - e.g. the people who post a photo of them outside their house saying 'off to France for 2 weeks'...telling everyone who sees it that their house will be empty!