I think of it this way: if a potential employer reads my blog and decides they don't want to hire me based on its content, I really wouldn't have wanted to work there anyway, and it's ultimately for the best. I would hope a potential employer would read my blog and make some sort of decision based on its content (positive or negative), because it's probably the best idea he's going to get about my likes and dislikes and my personality in general... there's only so much you're going to get out of an interview. Not getting hired due to blog content may be a liability in odd times of desperation, but I haven't run in to many of those in the past ten-odd years; hopefully my luck remains steady. In the meantime, I'll just keep writing.
And there's the opposite factor: Writing provides opportunity. I've maintained a personal web site with projects, disseminations of knowledge, and personal ranting (although that's rarer over time) and eventually the site has gotten pretty decently popular. And the number of random job opportunities has gone waaayyy up. If you don't write, you may be able to sneak more easily into a company, but it probably won't be the one you're really looking for.