[akmiller]

Then I want to email the link to that page, so I have to open the full Safari, then do the email link which opens my mail client, then close the mail client which goes to my home screen, go find my twitter app and open back up to pick up where I left off!

I like my iPhone but it has it's flaws just like any other device.

[siglesias]

You're wrong. http://yfrog.com/1ssz0p

This is a free app. It's up to the app's designer and isn't endemic to the device or OS, unlike the inexplicable permanent presence of a physical back button on Android devices.

[awolf]

Nah, Tweetie (the iPhone Twitter client in the screenshots above) also has a built in email client for sending links. No need to leave the app.

And yes in iOS 4 if you DID need to exit the app it would be in the state you left it when you returned.