The Register: "But a programming error by the search engine has compounded the problem: by inadvertently blocking thousands of sites from Google users.

It's been called a 'Google-NACK': you enter a particular search term and Google tells you that there are thousands of matching results, but fails to return many, or any results.

For example, a search for keyboard bracelet returns just five sites out of 'about 49,900'. (Your mileage may vary, as Google results differ depending on where you are, and which way the Segway scooters are pointing - but it's a fairly typical figure.)

What's happening? Award-winning researcher Seth Finkelstein has a theory why. Google's own spam filters, designed to weed out link farms created by pornographers and spammers and Scientologists, are crude, and are blocking many innocent sites.

'Technical solutions may have unintended consequences,' he says. "