When I was asked this question, I thought "interactivity" immediately. People have more opportunities interact with other people and also with technology. However, don't people interact with others with traditional media? What kinds of interaction with technology can be called "interacitivity"? Is this "new" about new media?
I am thinking some online games, such as mah-jong and poker. When I play mah-jong online, I can choose characers I would like to be, change colors of outfits, decide which rules I would like to follow, and also chat with my friends online. I interact with the computer, and it responds to me what I want. However, what I play and how I play are still as the same as I play with friends face-to-face with traditional ones. Will I play this game with another kind of "new media" in the future?
Time changes. Within different era or generation, how people present information is different with different inventions. Maybe "new" media just means only for people is a specific time, so new media is historicized. People change or invent various formats to reinterpret something which is presented in traditional media. For today, mp3 and digital formats are new media comparing with disc and tape. Youtube is new media for people today to broadcast themselves, but it will become old media when new "new media" is invented.
For today, I think what is new about new media is unicersal access to information, communication, and participation. Information is no longer accessed in one way. People can communicate through accessing the Internet or may different ways. In addtion, with this accessibility, people build up networking, share, and contribute knowledge all together. And I think this is new about new media in our time.