I see a lot of these on eBay and here in the shops in Bangkok... but I have no idea where they come from. They're still in the sealed boxes too. Does anyone know which carriers do not "brand" their Blackberries?

Thanks!

All Carriers Brand their phones. (only a few phones have exceptions)

You can get SIM FREE UNBRANDED phones from places like amazon, and other online "unlocked phones" sites.

RIM (and other phone manufacturers) make SIM FREE phones, which come with no branding, and are unlocked, because they know people will want to buy them, sell them on or use them etc.
For example, Nokia do SIM FREE UNBRANDED phones and you can buy from them direct. RIM however, don't allow to buy from direct, but do do SIM FREE phones which they allow other companies to sell.

There are only three models I know of that RIM sells directly to the consumer. See here:
BlackBerry - Buying from Research In Motion

Carphone Warehouse sells 'em unbranded.

I know that in Thailand, all three major carriers sell all their phones (including Blackberries) without any logos or branding. In MBK (with a whole floor of a shopping mall dedicated to small shops selling cellular phones), they are selling unbranded Bold 9700s which were brought in (grey market) from somewhere. I was just curious what country carries the new Bold that they are going to... it must be somewhere in Europe or Asia... they are definitely not getting them from RIM direct. Food for thought.

Thanks for the ideas!