It's only unsafe if you're dumb enough to fall for the links that can give you viruses. If you only use the Facebook site and don't go to separate links or ads hosted on the site, you'll be fine.
They make it to hard to set the privacy settings properly and applications have to much controll. Their incentive is to make it hard to keep stuff private.
I think Facebook is making an effort to improve security. I can now log in using https. Also, once I log in with my password, a code gets sent to my cell phone that I have to use in addition to my user name and password. Then I have to enter the location of my computer, which I had previously specified. If all these bits of information are not correct, I am not allowed to log in. Every time someone tries to log into my FB page, a note is sent to my e-mail address notifying me, with their ip address.
There are somethings that make me mad about ***** starting trouble with other friends & family. Example: The link about what you say about others...unlock now to see there comment, then makes you talk crap about others to see what they had said about you. I seen alot of fights take place like this. That Link needs to go!
People need to be carefull upon what photos they have and what they like. businesses are checking profiles before hiring now so watch drunken photos. And in the future likes will be used for personalised advertising, your privacy and data is wide open. Be carefull!