I've known some people first hand who've had their blog cracked and linked back to them. I've also seen people taking down their LJ accounts, which can be locked down (i.e. friends only) only to retain their Fetlife accounts which are fairly open by comparison.
Facebook is the antichrist of precautions in that their model is that everything should be freely available to increase the networking on the site; "Hi. I noticed that you also collected arrowheads. We should chat and become a target for marketers of arrowhead display devices." This inner relating of random things can make you a target ... and in being a target, be sale-able to facebooks customers -- the ones actually paying money to facebook.
If it's illegal, it can get you in trouble. If it's embarrassing, it could get you in trouble. If it's anything you wouldn't want your parents to know about when you were 15, it can get you in trouble.
Trouble you say?
Yes, such as:
- loss of a job you really wanted and were perfect for except that they were looking for ways of tossing applicants and that shot of you on youtube projectile vomiting put you out of the running.
- having your spouse toss out those snapshots of you that you never though would see the light of day in a divorce proceedings when child custody comes up.
- having your parents decide that if THAT is how you're spending your college time, they are not paying for it.
- finding that your federal job isn't secure after your boss gets a link to you smoking dope.
- discovering that 10 years of solid achievement at work kind of dissolve once everyone's seen you in your pony gear or in butt-less chaps in a pride parade.
Black Rose has relaxed some, but for many years we were told to not go up to someone we'd seen at an event if we were out in the vanilla world. You never know what will cause them concern and we were advised to never be the source of it. "Oh, so where did you two meet?"
If you meet online and want to meet in person, do it in a public place and don't give your name and address to them right off. Get a sense of them as a person first.
I've talked to fairly convincing men online who pretended to be women. If people can pull that off, how hard is it to be hide less obvious things about themselves? Get to know them. If you are not good at figuring out who's trustworthy find a wing-man who is trustworthy and bring them to at least the first meeting and listen to them when the meeting is over.
Use a little discretion. Don't use your work e-mail when ordering a strap-on or joining a bdsm group. Get yourself a yahoo or a gmail account.
When you use an e-mail address in your non professional side, don't list it as an alternative in your facebook account. If you give me firstname.lastname@example.org but also list that as an address in facebook, I probably now your real name and a lot of your friends.(And if you've used that "find your friends" feature in facebook, Facebook has helpfully added that e-mail account to your facebook account so that I can use it to find who you are. If I have your real name, there's a good chance I can figure out where you live. If you've used the address on Linked-in, I know where you work.
So does anyone else you give that address to.
Limit 'The real me' sites to a straight e-mail that you never use for kink or related activities.
I've met a lot of great people in the scene and at least 2 stalker types.
It was common knowledge among the White House Press Corps that Kennedy was seeing women on the side. It was part of the expectations that these things were not going to be made public. That age is LONG past. Somewhere there is a reporter or a blogger who will think they've hit the mother load if they find out what you did last Saturday night and that the thing to do is put it in print somewhere.
Be careful of what you leave out there for them to work with.
When in doubt, keep things at arm's length.
And, "Hey, let's everyone be very careful out there."