I agree with the main idea of the concept... but in my opinion the best implementation wouldn't be triple-click (like someone already said it, misinterpretation by the iphone, and become more sluggish)... and definitely not a button "lock" on every single application that uses landscape mode... it'll make the screen even more crowded... and about putting as an option in "Settings" is gonna make make it a pain in the butt...

... i mean what if i have it turned on (locked) because im lying sideways on my bed listening to music and dont want to turn into cover flow... and suddenly i want to lie on my back and watch a movie... what shall i do?
1. go to settings
2. turn on "lock accelerometer"
3. go to Music
4. Skim through my songs and listen
5. lie on my back
6. go to settings
7. turn off "lock accelerometer"
8. go to Videos
9. Watch a movie in Landscape...
it reminds me of my old windows days... click a thousand buttons to get a simple option...
the best solution would be, to be able to "lock" the screen by pressing the home button for 3 seconds and as a result the screen will shake slightly and lock. and u can unlock it by doing the same thing or by quitting the app. it'll be way less of a hassle because im not quitting the app to disable/enable and the single-click home button wont have to way too much to check whether u're gonna do a triple-click
let's go back to my step-by-step and compare...
1. go to Music
2. press the home button for 3 sec.
3. listen to music
4. lie on my back
5. go to Videos
6. watch a movie in landscape
(assuming im on an ipod touch because i switched from the Music app to the Videos app. And if im on an iphone it'll be an extra step to press the button for 3 seconds when i lie on my back to turn accelerometer on again)
what do u all think???