"These can chart experiences at work (earning some of their writers the sack)..."
("These" are blogs). Does it mean that "their writers" were sacked?
In advance thank you for answering me.
So they get sacked because they were writing their postings on the blogs instead of working?
I see. Thank you very much indeed.
Most likely the employers were angry about the negative comments the employees posted on their blogs, but there is not much they can do legally about that (freedom of speech and all....). So the employer would use the excuse that the employee was posting on company time when he should have been working, and that's why he was fired.
("Got the sack" is strictly BrE usage. In AmE we say "got fired" or "got canned.")