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Either way, it seems the vast majority of the posters here would prefer a 4.5 inch screen.
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Wow, biased much? According to your own poll, only 55% of posters here prefer a larger screen. That's not a "vast majority". Also, as someone pointed out, this is a small sample of the total iphone market (less than 1%), and it is also a BIASED sample, being a technology forum. You are correct that "most other polls are done with small samples of the whole market", but you're forgetting that those polls are done with uniform unbiased samples. In fact, marketing agencies go through a lot of trouble to make sure the sample population is as well-represented as possible. That means they poll people like us (techies) AND non-techies AND old people AND people who don't frequent internet forums ETC...
We all know your opinion on the subject but since you started this thread to get a feel for what people are thinking, you should try to be a little more impartial and respect peoples' opinions even if they don't agree with you. For example, you can't say that the black bars on the iPhone are "wasted space" because they DO serve a purpose: so that you can hold your phone (to play games and such) without obscuring the screen. It's the same reason that apple intentionally put the thick border around the iPad. It's not that they can't bring the screen all the way to the edge, it's that they built-in an ergonomic way to hold it without interfering with what you're trying to do on-screen.
To me and many others here, I like the iPhone how it is. I wouldn't want to make it any bigger, and I wouldn't want to sacrifice that valuable holding space. You may not need that space, but other people do.
The bottom line is this: Apple doesn't "guess" at these things. They spent (and continue to spend) millions of dollars on marketing research to see what the true majority of their customer base wants. This data isn't published, but we see the results in the products they release. If they don't release a larger screen iPhone, it's because the majority of people in the world (not in some online forum) don't want a larger screen. So you can go ahead and email Apple all you want. Until you become the majority, they aren't going to change it.