I'm just curious if anyone has registered their unlocked iPhone with apple?

I'm usually religious about doing this, but I'm not sure that an unlocked phone will be covered by any warranty, so not sure if there is much point.

The only benefit I can see is if it somehow told Apple just how many international sales they've been getting, and how preventing them from being unlocked will reduce that in the future.

However, since few international people will be doing that (out of paranoia!) the figures wouldn't tally anyway, so there's probably not much point.

Even people in the US who have "hacked" the phone (usually by unlocking) have lost their warranty and the Apple Stores are refusing to fix them.

I did it.

I don't expect to be covered by warranty, but I just did it anyway.

I always register my products, so I figured why not. Of course, I can simply say that it was purchased in the US by a family friend (not really true, I got it off eBay USA) but I don't think any harm can come (touch wood).

Wrong move...expect steve jobs to show up at your front door with a nerd stick containing firmware 1.1.1 which he will flash your iPhone with while you are restrained...

I didn't even know we were supposed to register products if we dont have applecare?

It just corrects the date of purchase (if it is different to the one in their database).

I remember my iPhone (checked serial at apple.com/support) and it said my iPhone was purchased 1 month in the future (!) from the then date.

Then once I registered, the date of purchase changed (to the date of product registration).

It is for warranty purposes (within the first year) even if you haven't purchased AppleCare. It also links the serial to you/your AppleID.
http://register.apple.com