Don't be an Internet Idiot.
My mom always told me and my sister when we were growing up: never write a letter or say anything on the phone that you wouldn't want to see on a billboard in Times Square. That advice has only become more pertinent over the years; especially now that people are being fired, losing their government assistance, and destroying the PR of their company by saying things that ultimately reach the eyes and ears of the world.
Of course, it doesn't all have to be negative--the examples above are just the most sobering way to make the point that people have to start viewing social media outlets as potent tools which can be the harbingers of doom or delight, depending upon their use. In "On Writing Well," the best book ever written on the subject of nonfiction writing, author William Zinsser makes it clear that the best way to write is to make it seem like you're having a conversation with the reader.
Since this conversational style of writing has become the norm for social media outlets, it's important to remember the difference between saying "Dude, I frickin' hate working for this bloated whale of a company, Microswift!" to a friend, and posting it on a blog, tweet, or Facebook update. The Internet is forever: you can't get it back. Sure, you can delete your post, delete your entire blog account, or even commit web 2.0 suicide, but the fact remains that what happens on the 'net, stays on the 'net. Forever.
Let's Talk Turkey
Now that you've been properly scared, it's time to talk turkey. The reality is, the blurring of the personal and the professional online doesn't have to be bad. In fact, it can be really, really good. No one wants to read your blog if you talk like some pompous fatcat that just wants ROI on their newly-minted social media PR/marketing blitz. People want to feel connected to other people, and the way to do that is to talk to them like you would in real life. That is, of course, assuming that you have manners and don't swear like a sailor.
If you use the social media platform to engage in real, unbiased conversations with people about your business or interest, you're generating positive vibes. Positive vibes will create ripple effects that can only lead to good things for your business or interest. The whole point of social media is to connect with people you wouldn't otherwise have been able to, and hopefully form some new relationships as a result.
So next time you're about to post something on a social media site, consider what would happen if everyone in the entire world read it. Would your boss suddenly get an itchy trigger finger? Would your girl/boyfriend be interested in a 'break?' Would your customer base feel like the faceless corporation you represent now has a face--and they kinda like it? The choice is yours, so think long and hard about what you say, and who you say it to. Otherwise, you could end up like these people. And nobody wants that.