Your example of tiny.small.big.bigger is the wrong way to look at it. Instead, look at it as http://<unique host identifier>/path/to/resource and it makes more sense. tiny.small.big.bigger isn't even correct since you're trying to map "size" to subdomain level. As if a subunit with 5 parents can't be larger than a subunit with just 2 parents.
And com.google.mail would mean specifying the least meaningful information first. Would you rather be introduced to someone as "Widgets Incorporated, Director of Widgets, John Doe" or "John Doe, Director of Widgets at Widgets Incorporated".
I agree. If people knew how to read URLs, then phishing scams would no longer exist.
"Okay, the domain in the URL for this link is X, but I know my bank's domain is Y, therefore it's a scam."
Part of it is the URL syntax being unintuitive, part of it is simple lack of proper education/training. But it seems like in the time you tell people "DON'T CLICK LINKS IN EMAIL OMG", you could just teach them how to read a URL.
Maybe if URLs had spaces and looked a little more like a postal address than a confusing jumble, people might actually read them. As it stands now, though, most people just type everything into a search page -- even if they're actually typing in a URL as a search term. Kind of like that story about the number one search term on MSN being Google.
And com.google.mail would mean specifying the least meaningful information first. Would you rather be introduced to someone as "Widgets Incorporated, Director of Widgets, John Doe" or "John Doe, Director of Widgets at Widgets Incorporated".