I think that the level of proofreading and editorial checking on just about every publication is lower than it was a decade ago. Every media outlet, whether it's a global news organisation or just a blog is under so much pressure to constantly create and push out new content that simple errors just slip by.
I'm constantly surprised when I'm reading something on a major news site and see typos or similar mistakes, I shouldn't be surprised anymore because I see them all the time, but it makes me a bit angry and sad every time I do.
I don't know how much search engines care about good grammar, etc. but as a site visitor I'm much more likely to come back / subscribe / buy something / whatever if the copy is written and checked properly.