The problems really begin when a browser doesn't want to wait for a standards body. I realize the situation is different with WHATWG now than how this played ou

The problems really begin when a browser doesn't want to wait for a standards body. I realize the situation is different with WHATWG now than how this played out in the IE6 days. But when the dominant rendering engine decides to start adding features where the standard hasn't caught up yet, you're arguably no longer doing web programming, but rather Chromium programming. This sort of thing boxes out other vendors/rendering engines and forces them to have to add non-standard features themselves. Vendor prefixes are not enough. If devs no longer test on non-Chromium platforms, vendor prefixes have to be adopted by non-Chromium engines or risk utter obsolescence. This is also true of Chromium forks. If a fork is a niche player, being open source doesn't buy you much because the Chromium governing body (i.e., Google) still has the lion's market share, and thus the decision-making authority for what the web should look like.