Even if reading an applicant's blog didn't raise legality questions with regard to whatever incarnation of the discrimination act is in force at the time, it's still an invasion of privacy. Professional and private life should be separate because things get extraordinarily messy when they're not. If a blog addresses a topic peculiar to one sector, then the other oughtn't be reading it, much less using it as an accessory to the interview process.

I'm all for some other, much more objective and tangible way of ensuring that a job candidate isn't a fucking idiot (such as the interview), and I'm tickled pink by any notion that gives internet people an employability edge over lesser mortals, but blogs aren't the way for either to be decided.