You gave me a great visual which got completely out of control in my head:

Imagine India read your message and thought, "Hey, if we just GO there and build an artificial island, we'd clearly be reamed by the international community... but if we LAUNCHED enormous granite boulders from India into the sea as part of, say, a scientific experiment, and they happened to land on that island and were big enough, we'd have sovereignty again!"

Then of course, Bangladeshi spies discover the plan and formulate a boulder launching initiative of their own.

There's a great boulder arms race, a frantic push to move boulders to the coast, boulders destroyed before they can be loaded by opposition spies, boulder transport sabotage, and when they finally reach the coast and the enormous catapults specifically built by whichever local contractor said they could get them done in time are deployed, the great boulder launching war begins, each launching boulders "harmlessly" as part of scientific experiments toward the same island at the same time, using catapults prone to poor accuracy due to the late contractor bidding and the fact that they were built in India and Bangladesh.

I can see the headline now:
Mar 29, 2014: RARE MID-AIR BOULDER COLLISION RAISING TENSIONS
Indian statesman quoted as saying "This is the fourth incident of Bangladeshi's clearly ruthlessly expansionist government interfering with our harmless scientific experiments through high-tech mid-air boulder tracking technology they have secretly been developing with neighboring terrorist states for years."

There's no lock in. You can list an app and leave the whole thing as third party with no integration with Google Apps.

If I'm some random Google user and I use Gmail, Calendar, and other apps every day, and I also use Joe's Hosted Task Manager, it would be very convenient for that to be in the google apps tabs and on my google apps domain.

I'm sure the rats feel nervous about leaving the sanctuary of their hidey holes and walls to get to the cabling. Why not load in a few miles of old cabling into the walls so they can eat it there and not have to come out? :)

So, someone has chrome.com too, no guarantee Google will even be interested.

Whoever owns gdrive.com would be wise to offer a backup service though :)

On reason being overlooked for web apps is that the app keeps running, doing things for other people, even when your system isn't.

So if we create one, you're saying we can't throw garbage into it and solve the world's waste disposal problems?