specifically iPhone4 – any reasons why not?

it costs a fortune?

I might have some scraps that are big enough – so free.

Isn’t that all most screen protectors are anyway?

Its what I’m using on a non touch screen Nokia and it appears to work fine.

Isn’t it really sticky so if u need to replace it, it might be a pain.

It also might stop a touch screen working? Or perhaps just make it a bit less sensitive.

I use it on my mobile and it’s works fine although I’m not sure that the optical clarity is as good as proper screen protector.

I’m guessing it’s a bit too thick to work on a touchscreen screen…also for proper stickiness you need to hairdryer it on – which suggests to me it’s likely to be ‘welded’ on and a right PITA to remove if ever needed…