The winner is Facebook, which takes the award for the most-blacklisted Website. No fewer than 23 percent of OpenDNS business subscribers consider it forbidden Internet territory for their workers.

Happily for Facebook, it's also the second most whitelisted Website, which is to say, it's a site that's permitted when most other sites are blocked.

Clearly, one man's waste of time is another's essential.

OpenDNS is a subscription service that can be to replace their ISP's domain name system (DNS) servers. DNS is what's used to convert human-readable addresses, such as pcworld.com, into the numerical IP addresses required by computers.

Most DNS servers simply duplicate master servers, but OpenDNS offers powerful filtering tools too. This raises the hackles of some but the fact is that OpenDNS is popular, serving 30 billion DNS look-ups every day and handling the DNS requirements of .