While it's true that Microsoft has done it's part to hold up progress, the fact is that much of what you love about the web today can be directly traced back to innovation at Redmond. Let's give them credit where credit is due. Hell, they came up with AJAX so people could access Outlook from the web. Do you remember how obnoxious browsing was before XMLHttpRequest?
It's an accident of history that's it's primarily used for Json and not Xml, but you can hardly argue that the API itself was an accident.
Frankly, the importance of json in this matter is pretty minor anyhow: if it hadn't been around, you can bet some nice JS library would have come up with a different way to easily decode server data into JS objects. The scripted communication was key.
While it's true that Microsoft has done it's part to hold up progress, the fact is that much of what you love about the web today can be directly traced back to innovation at Redmond. Let's give them credit where credit is due. Hell, they came up with AJAX so people could access Outlook from the web. Do you remember how obnoxious browsing was before XMLHttpRequest?