Proto-earth, dinosaurs, and the days when your personal and business profiles were separate and distinct. What do these things all have in common? They are all in the past.
Corporate background checks now routinely include a search for social media profiles, forum posts, and blogs. As professionals are learning, the things you say and do in your "off-work hours" can and will be used against you - even after you're hired and have been doing the job awhile.
One point? Be careful what you put online. That stuff never goes away (<-- the company website for a small business I ran from 1994 - 2001). There are a couple approaches to managing your online image:
Keep track of your public persona. Shape it. Manipulate it. Second-guess every Facebook and LinkedIn update and tweet; or
I like the second option.
I checked my watch just now and it's 2011. I think we're all past the time when it's-not-personal-it's-just-business is an acceptable excuse for treating someone poorly. But if that's where you are, you may want to choose option 1 above. It's a lot more work, and you will eventually be found out, but it may protect you for a bit.
Being you isn't without risk. You will lose opportunities because of you. Some will not be comfortable with your views on something or other, others will be uncomfortable with your openness. Transparency isn't easy and it isn't free. Some find it intimidating and that's ok.
A Little Secret
There are more fish in the sea. There is enough work out there for you to shop around some until you find a good fit for you. There will be new projects dreamed up tomorrow, next week, and next month. You don't have to change who you are to avoid starvation and bankruptcy.
In other words, you will be ok just being you.
Be who you are.
Do what you are.