Lots of strangely negative reactions here. We (http://inky.com) think this is a positive development and plan to support it as well. We're happy Google has promoted open standards in doing this.
I want my email to be a consistent experience - not to get some different behavior if I access through a certain device. Email and its simplicity was universal - I saw the same text on my phone, tablet, laptop and desktop. Will every mail sender who makes use of this, include the JSON and an alternative link to achieve the same result. I think this could get very inconsistent very quickly. Fragmenting email is not something I like the idea of.
For Google Apps customers' internal mails I think this is useful. For the wider Internet I don't like it.
What's nice about what they've done here is that they've required an additional (but now standard) level of authentication for the senders who want to include this richer, more actionable content. And they haven't hardwired this into Google Plus or some other walled garden. That's welcome, IMO.
CSS is a complicating factor as well: some CSS is unsafe and must be stripped, which requires a real (error-tolerant) CSS parser to go along with your real HTML parser.
And identifying remote images: you'd think that was easy right? But do you know how many ways there are to reference a .png image in HTML and CSS?
At one point Facebook emails were even hiding web bugs in BGSOUND tags -- sneaky!
I agree a standard set of HTML and CSS for email would be a huge benefit.
It was only afterwards that I started noticing most beautiful emails are just sliced images displayed within tables. Thats right, tables.
Google Reader drama isn't ever going away on HN, is it? The loud minority keep bringing it up regardless of what innovative products Google develops.
> I want my email to be a consistent experience - not to get some different behavior if I access through a certain device.
One decade ago most clients poorly supported HTML email, if at all. It was an inconsistent experience. Understandably it was new technology, so most of us patiently waited until the standard was adopted by email clients.
Same thing here.
Actually, its to make machine-parsing of meaning easier so that information can be extracted from email and presented through other UIs (particularly, Google Search and Google Now.) Surfacing and facilitating responses to calls-to-action in the Gmail UI is important, but the big motivation is, I think, found in the two pages in the "Cross Google Experience" section of the documentation for the Schemas in Gmail feature [1][2].
[1] Answers in Google Search: https://developers.google.com/gmail/schemas/google-search [2] Google Now: https://developers.google.com/gmail/schemas/google-now
Good marketing bit there ;)