The Sun Online - Bizarre: Posh who? says Britney

The Sun is outraged and surprised that Britney didn't recognize the Beckhams

This gives you an example of The Sun's cluelessness, not Britney's. The Beckhams could walk unnoticed and unrecognized in just about any city in America. I would know who the Beckhams are if they introduced themselves to me, but I wouldn't recognize them on sight if they were in my own living room!

I would bet that if you asked Americans about them, about 5% would know who they are (vaguely), and about 1% could look at a picture of either of them alone and produce a name unless aided and prompted.