After reading through the threads, I set up an account just post here.
I use my iPad every single day. I'm a freelancer, I work with my laptop and do my browsing/research on there.
My iPad is mostly for reading newspapers (newsapps), calculator, radio, ibooks. I browse through my email first thing in the morning on my iPad so I know who I've got to reply to workwise on the PC later, and then I read emails from family and friends.
When my young daughter's here, she monopolises it for games. When I was single and my daughter was still learning to read, the iPad suited my needs fine. But now my new GF uses it for Facebook/YouTube and my daughter is a little older, techsavvy and curious. I don't feel comfortably with them being able to read all my emails whenever they want, but nor do I want to deprive them the pleasure of using the IPad.
The argument that Apple hasn't/won't password protect their native email app because the device is only meant to be for a single user is ludicrous. Of course they know all family members are gonna use it when it is a household device.
As many have pointed out on here, users can password protect/restrict Safari, camera and other apps, so Apple obviously also recognise the device owner may not wish to have users browsing and taking photos, etc.
So why not email?
Some people have suggested that Apple want to force us to buy devices for the entire family just so we can protect our emails. Maybe, maybe not. I think not.
Another possible explanation is that companies may wish to supply iPads to employees as a work tool on which email access is necessary but browsing the web and taking photos isn't. Take a look at which in-built apps can be password protected/restricted and from this perspective it makes sense: music/downloading music, deleting/adding apps, adding personal e-mail accounts, YouTube, web browsing, etc. In short, the restriction options allow companies to block any personal use and turn the iPad solely into a professional work tool.
Even the fact that the iPad user can have the general pin to slide to open and the company has the pin used to configure the device. Want more? Setting up new (read employees' personal) email accounts can be restricted but the email app not.
Also, if Apple only thought about making more money, why would they allow iTunes to be blocked? iTunes makes them billions, e-mail makes them squat!
I'm not a blind, dewey eyed Apple freak. I still use my iPad 1 coz until recently it suited my needs perfectly. Back when I bought it there were no other tablets on the shelves. But when it comes to updating (I recently got a small crack on the screen), I will definitely look at other (Android) tablets and if they suit my new needs (i.e. older, curious daughter and prying GF), I won't think twice about buying one.
So, no, I don't think the lack of email restriction is Apple trying to manipulate clients, I think it's Apple not taking the competition serious enough and resting too much on its laurels. Apple's current capital might was created on the back of its totally new, innovative devices launched during the last decade. But it appears the hard tech for new, game changing devices has been exhausted for the time being and the current market is all about perfecting existing products and services.
Apple better start listening or it will be the next Microsoft, playing catch up to Samsung!