I don`t do Twitter but I dip into facebook. Like all tools, facebook can be useful or damaging but there are easy steps you can do to make it safer. Keep your account private, only allow people you actually know to befriend you, . . . .
While this is certainly good advice in principle, never to befriend anyone you don't know severely limits the experience and benefits of FB. I don't use FB for communicating with people I already know at all, if I can call someone on the phone or see them at work then I don't befriend them on FB. I use FB purely as a tool to pursue my real passion in life, that of animal rescue and welfare. I've never actually met any of my FB "friends" in person, but they've all proved themselves as animal advocates and have shown that if I ever need their help with anything all I have to do is ask. I know they are who they say they are because others have met them and visited them while transporting dogs and cats around the world. Most of them have adopted dogs themselves, so have had to provide personal details and copies of passports to other members who are shipping the dogs. It's certainly true that you should take care who you befriend on FB, but it''s also true that FB can introduce you to wonderful people who share your loves and aims, and who can enrich your life enormously. I've met people I know I'll be friends with for the rest of my life.