Is there really one way to email successfully?

I’ve been watching a bunch of folks discuss someone’s mailing practices. The discussion has been fascinating to me.  I’m hearing from the conversation is that there are very specific rules regarding how every company should mail. And that anyone who deviates from those practices is heading down the path to failure. Doing it wrong.
This theme has come up before, when I’ve heard expert marketers comment that Groupon proved how wrong the “daily email is too much” advice was. My response to that is confusion. Who decided daily email was too frequent and wouldn’t work?
I come from a non-marketing background, so maybe I’m missing some essential bit of wisdom or context. But it strikes me that a lot of the rules (no daily email, never establish aggressive engagement metrics) are really stifling innovation. There seems to me to be an unwillingness to think about why it might work if a particular sender does something against the grain.
Of course, once something has proven a success, everyone jumps on the bandwagon. Half my potential clients over the summer told me they “want[ed] to be the next Groupon.” Most of them didn’t make it, though.
I look at email as having a massively diverse user base. There are lots of people who use email in ways I would never consider. There are lots of people who think the way I use email is wrong. Unlimited opportunities for smart marketers exist.
The more cynical part of my brain says that finding and developing an enthusiastic recipient base takes too much time. Companies want to be the “next groupon” or the “next facebook”. But they want to do it by copying the business model, not by being innovative and meeting some need that currently isn’t being serviced.
There are, of course, some models that are never going to work, like randomly harvesting addresses and sending spam. But I don’t think that means email marketing is dying, just that innovation and imagination might be.