Oh yes, it is true. I had never noticed that feature!

Do MX player lock works on all apps or only when you have mx player running

how about when you browse and watch Flash movie on flash website

I am looking for ways to prevent accidental button press ..

pressing the power button turns off the screen as well.

It's not on all the apps. But some do, like MX. Maybe this stuff should go on the android design site

you mean each app developer has to keep this in mind?

maybe I can suggest to youtube, skyfire and dolphin browser app to add the feature

other reading app .. where you can spend a long time on one single page.

I think YouTube kindaa has this. Where I think if you don't see the controls any more, you have to tap the screen once to activate the controls before you can use them.