My social media presence:
Sometimes I tweet a lot. Sometimes I tweet a little.
Facebook: Janet Stemwedel
I generally only accept Friend requests from people I "know" in some robust sense, although not always in a real-life context.
LinkedIn: Janet Stemwedel
I only accept invitations to connect from people I actually know in a professional context. (If we met at a conference, it's helpful to remind me of *which* conference if you ask to connect with me.)