Trashing may be too strong a word, granted. But it's making public unflattering internal details about a company that employed him. I would be personally irritated if I was this guy's manager.

Coming across material like that when researching someone for a job would probably be a no-hire flag for me - and many others. I'm sure he's a great designer, but does a post like that expand or limit the number of future gigs he might get? You could say "he wouldn't want to work at places like that anyway", but I'd rather have that decision left to me rather than a lack of response when I'm looking for work.

Offering this in the spirit of advice. I've been hiring people in the valley for 10+ years. I used dejanews to screen applicants prior to google... today yes we will read your tweets, find your blog, and skim it all to get a sense of who you are. Be thoughtful about what you post.