More than a quarter of respondents -- or 28 percent -- admitted spending less time socializing face-to-face with peers because of the amount of time they spend online.

It also found that 20 percent said they spend less time having sex because they are online.

Cell phones won out over television in a question asking which device people couldn't go without but the Internet trumped all, regarded as the most necessary.

"It is taking away from offline activities, among them having sex, socializing face-to-face, watching TV and reading newspapers and magazines. It cuts into that share," said Mack.

"I don't suppose their partners are too pleased about it."

Mack said a clear trend to emerge from the survey was the increasing need for mobility with people no longer satisfied with just broadband access from home and wanting hand-held devices like iPhones and BlackBerrys.

1. Wuthering Heights by Emile Bronte
2. Pride and Prejudice by Jane Austen
3. Romeo and Juliet by William Shakespeare
4. Jane Eyre by Charlotte Bronte
5. Gone With the Wind by Margaret Mitchell
6. The English Patient by Michael Ondaatje
7. Rebecca by Daphne Du Maurier
8. Doctor Zhivago by Boris Pasternak
9. Lady Chatterly's Lover by DH Lawrence
10. Far From the Madding Crowd by Thomas Hardy

There have been major changes in the rankings this year. The winner: San Francisco, up from fourth place. It ranked first for culture and received high marks for number of singles, nightlife, online dating and cool. The "city that never sleeps," New York, N.Y., came in a strong second place, thanks to its performance as the country's No. 1 spot for nightlife. Entertainment mecca Los Angeles came in third, Atlanta fourth and Chicago fifth. Rounding out the top 10 are Washington D.C., San Diego, Seattle, Dallas-Fort Worth and Philadelphia.

Denver, meanwhile, our top-ranked city from 2004 to 2006, has dropped to 16th place. But before Denver city elders start beating themselves up over this, we should note that this is largely because, amid several refinements to our methodology this year, we've switched to a new way of defining each city. In the past, the boundaries and population of each city were drawn from the U.S. Census Bureau's list of "Metropolitan Statistical Areas." But in 2007, we've begun using the Census Bureau's "Urbanized Area," which provides a tighter focus on cities themselves.

1. San Francisco-Oakland
2. New York
3. Los Angeles
4. Atlanta
5. Chicago
6. Wasington
7. San Diego
8. Seattle
9. Dallas-Fort Worth
10. Philadelphia