I have my blogs flow into Facebook. This one included. Since much of what I say, in long form, is said here, it makes it easier for me, and for readers. Each post heads in as a link, with a few sentences, maybe a picture.
Otherwise, I use Facebook for a mix of personal and professional dialogue. Same with Twitter. I don't accept followers who do not have a real connection with me. If an unknown person follows me, I might write and ask what our connection is. Sometimes I will connect, having found they are genuinely interested in me as a writer. Otherwise, I ignore them. I mean no harm or insult, but I cannot keep up with everyone.
If dialogue gets too raw (usually extremists on either side of political spectrum), I delete the comment, and if that friend insists on raging on my threads, I unfriend them. No love lost, but my account is family friendly. They are free to be who they want to be, but I am free not to expose myself, or my friends, to nasty attitudes or language. I used to work at a HS, and have lots of teens as FB friends, not counting younger relatives, and choose to keep things clean and friendly in my house, so to speak. The kids will hear whatever elsewhere, but not in my area.
My privacy on Facebook is high, almost 100%. I can be found, but generally, it needs to be someone who already knows me, or, knows someone I know. Maybe they see me post on my HS alumni group on FB or some other group.
There are people who follow anyone for who knows why, or to garner some advantage in one of the mob or farm games. I only play Bejeweled or chess, so 10,000 followers are not needed there.
In the case of Twitter, I regularly and aggressively block and report as spam followers who are spammy. This includes any follower that is into MLM, 99% of real estate and financial sales, and those who claim to be some kind of expert in social media. If I see lots of Amazon links, or bit.ly links in most posts, I become suspect. I make money off of people buying through Amazon from my links, and from Google ads, but in Twitter, I have 140 characters. If all I am is a sales pigeon, move on, or, I will move you on for me by blocking you. I want genuine dialogue, not sheer marketing.
In my Twitter account, I most often post things of literary interest, or about running. I follow runners known and unknown and book industry people, as well as friends and colleagues.
One red flag is if they follow many others by the time I see their e-mail. If the e-mail says they are following 500 people, but when I see their profile, they are following 600, I know I just came up through a keyword search. Occasionally, someone useless sneaks through, and I delete them later, or Twitter realizes this and deletes them for me. I am more tolerant with Twitter about the depth of relationship because I am far less personal there, and someone can follow me with me having to do the same. My Twitter account is linked from my website, implicitly inviting anyone to follow.
Any follower on Twitter must jump through a hoop, reducing some spam. It isn't perfect, but it helps.
LinkedIn? I'm there too. Plaxo as well. I use Plaxo less, but both are almost purely professional. As social networking go, I have only so much time to attend to maintaining them, and so those get the back burner. I delete LinkedIn connections periodically, after realizing they are 'job coaches' with "Linked In Open Networker (LION)" in their name, only trying to use me to gain business I have no interest in assisting. I will connect with select unknown people, but your cause must be noble. I also accept chocolate chip cookies. That's an especially noble cause.
If you think we might have a potential business relationship, look me up. No, 'business relationship' for me does not mean selling vitamin juice, or getting my friends to sell detergent.
So, follow me, if you dare.