Unfortunately...
...for me, and I suspect most people, having a separate keyboard just isn't practical - I'm hardly going to stop and sit down just so I can type a quick text message or email...
I have an Apple Bluetooth Keyboard for my Archos tablet, which is fantastic, but it's fantastic because I'm normally typing on my tablet when I'm sat down on the coach/train/bus what have you and have somewhere to rest the tablet...
And for what it's worth, folding keyboards are incredibly tricky to get hold of, expensive, and from my experience not of that good quality.
It really is a shame that decent phones with decent, proper keybaords are so rare...