I blog for SEO purposes but find it a time-consuming once-weekly chore

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If the blog item doesn't pay off in a Google pge 1 rating - at least for a short while - I really resent the amount of time I've spent writing it. It's also difficult - for career advice sites at least - to build a "community".
Being less negative for a moment, I've also found that blogging leads to you making potentially valuable contacts you might not otherwise have had. The contacts may come from comments on the blog or the writers of other blogs you stumbled across when trying to find out how well your own item performed in the search engines

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Contributing to other sites' blogs can be useful publicity, I think. As CareersPartnershipUK I contribute to many much bigger career, job search and general readers forums (eg the Guardian, Prospects, GraduateFog, etc). Using your company name as your screen name makes it easy for readers interested in what you've said to look you up - and they do. Obviously you do have to be careful to stay within the rules and not tout too obviously for business.
You need to be able to control / edit comments to your blog. I've had loads of incoming spam (some of it appearing as harmless generic statements along the lines of "great article -keep it up"). My bugbear at the moment is huge lumps of spam appearing in what seems to be one of the Eastern European languages.
Otherwise, I "approve" anything which seems relevant to the blog item itself, including those comments with links back to other sites (though I check those other sites first!!).