Yo, Philly, U sure tweet a lot

That leveling power again. Harte says that "through Twitter, you can get through to a CEO who's into tweeting. They know the culture, they'll forgive the misspellings and grammar because they know the culture, and they'll answer your questions in that spirit."

Brown agrees: "CEOs and higher-ups who control millions of dollars, they're using the slang and shortcuts of the tweet. It definitely levels the playing field."

A shelter from zombies

Mia Gannon, advertising and promotions coordinator for the Art Museum (No. 10 on the list), says: "We've had to learn to loosen up on our tweets and speak the language of social media. We can't just post our calendar listings. We have to be more personable. And once we did, we really started building up our following."

One follower, she says, blogged that the museum was the safest place in town in case of a zombie invasion. She answered him playfully; it was retweeted, and more people became followers of the museum.

The social-media world, and its merger of public, private, work, play, business, and pleasure, comes through loud and clear when Shamara, between songs, says, "Anything else you want to hear? Pick up your phone and tweet me!"

Contact staff writer John Timpane at 215-854-4406, jt@phillynews.com, or twitter.com/jtimpane.