What we find bizarre is that it's such a strict lock-out, and that you're not given any degree of choice in the matter. It seems so weird that anyone can access any region's PSN Store, but not the online social networking hub. We can only assume that similar restrictions as on the store will be made for purchasing within Home. That is to say, if you're a UK credit card owner you won't be able to spend anything in the US Home without some jiggery pokery.
Obviously, this all makes sense to Sony. Home is meant to be a big income generator for them; mostly through advertising. They want the most appropriate eyes to see these adverts in order to maximise the "click through" rate. There's no point advertising Mountain Dew to a UK citizen, for example. But console-specific region locking is not the answer. At the very least, set up an IP location check or, god forbid, give people a choice.