A reader wrote asking if I knew of a business example where somebody provides restricted KML files to Google Earth, i.e. which require a user ID and password to download (the idea being that you could then sell them).
That’s not possible, as far as I know and the reason is that Google Earth does not currently have the ability to ask for user IDs and passwords before accessing a restricted server. (I could be wrong, in which case please set me straight.) [I am wrong. it works fine. See comments, and I have word from the Google Earth team as well. (20:30 UTC)]
It is not an outlandish feature request, though; the nearest analogy is RSS, and RSS readers are definitely able to ask for passwords, and there are restricted RSS feeds that require it.
In the meantime, vendors could keep network link files they want to sell on a restricted server that you use an HTML browser to access; these then get downloaded and opened in Google Earth, getting their data from normal, non-restriced servers. Of course, people who download a password-protected network link would be able to just distribute it at will, but you can do the same thing with passwords for normal content. The trick, then, becomes making sure the network link refreshes from a URL that has unique ID linked to an account. If an account starts getting hit from many different IP addresses simultaneously, you could call it abuse and cut it off.
Regarding business models and Google Earth, the only ones I’ve seen so far are referral-based (use our Google Earth network link to find a hotel/house/holiday and we get some money), services-based (let us build you your Google Earth-based web app), as advertising (Google Earth is impressive, so is our product/city) and tangentially, as content producers (3D models that could be viewed in 3D renderers, including Google Earth). but I haven’t yet seen anyone deliver value through Google Earth for an up-front fee. One of the easiest Google Earth-based applications to monetize in this way right now, in my opinion, would be a game, like GEWar.
[Update 12:38 UTC: I soon as I posted, I thought of an example! Geocaching.com makes its geocaching database available in Google Earth for premium members only. It’s one feature among many you get for $3 a month.]