Your question, I think, is less about changes in English usage than about changes in publishing. As StoneyB notes in a comment above, copyediting is far less common on the Internet than it is in print publishing—and so is proofreading. This reflects a couple of realities of online publishing:
Mistakes are not set in stone (or papyrus). If some aggrieved reader points out a particularly unfortunate typographical error or factual inaccuracy, the publisher can reenter the story and edit out the mistake. It's just like having a copy editor (for that one change), only cheaper.
Very few publishers make a profit from online publishing (or at this point, from print publishing either). And this sad reality leads to some rather desperate decisions about what constitutes acceptable-quality content for publication. Under the pressure of dismal financial results, a publisher's management team suddenly sees things like copyediting and fact checking and proofreading (all of which were standard functions a decade or two ago at most mainstream print publications) for what they are becoming: unaffordable luxuries.
The hard times that the publishing industry is suffering through because it can't figure out how to make money online without reducing its editorial staff to a skeleton crew has a carryover effect on print. Most of the money that a print publication generates comes from ads, not from reader subscriptions—and now most ad dollars are moving to the Internet (where the direct contribution of the publication's readers to its profits is practically nil) or out of publishing altogether, which means that quality-control staffers on the print side look more and more like luxuries, too.
Also, in the long run, the lower publishing standards online tend to diminish readers' expectations of publication quality in print: If you're accustomed to seeing unedited or cursorily edited content online, it won't be as jarring as it might once have been to see such content in print.
So far, I've addressed only the professionally produced content online. But as Hot Licks observes in a comment above, a lot of the content you see online isn't professional in any way: It's generated by people who write a blog or post to Facebook or tweet on Twitter for the sheer fun (or outrage, as the case may be) of it. A reasonably well-informed professional writer might be embarrassed if you pointed out an instance where he or she had used the phrase "I need to breath." So might an amateur—or the amateur might have no idea what the problem was.
For a couple of centuries now, copy editors and proofreaders have exerted an extraordinary (although mostly invisible) standardizing effect on published content—on spelling and stylistic consistency, of course, but also on word choice, syntax, and general coherence. It will be interesting to see what emerges in their absence.
