Brianstorming - what others are " "ing now?

My thesis focuses on "Web 2.0 Apps in Mobile Context"

What is Web 2.0 App? I have a very personal and not well defined view point that it is a platform satisfying human's curiosity. For instance, digg is a platform that you can know what others are reading now. Twitter is a platform that you can know what others are doing now. Facebook is a platform that you can know how and what your friends are doing now.

The Web 2.o Apps now are developed for the unique context for instance we use it at home or office individually and only focus on doing it. There are increasingly people using mobile phone to access internet. The context we use internet is dramatically different for instance accessing internet is more on-the-go, within a event or with others together. There should be some essential difference between accessing internet on mobile phone and pc.

Web 2.0 Apps in Mobile Context means a platform you can know something others are doing now in mobile context which is different from context using pc. Therefore, I want to do a brainstorming what do you want to know others are doing now and in what context? This could be very simple, for instance I want to know which store nearby sells great and cheap vegetable, which restaurant has good "today special" or which art piece is popular in the museum.

Brainstorming questions:
Please write down your favorite web services / applications with one sentence that it makes you know what. ex Twitter is a platform that you can know what others are doing now.

In the mobile context which means on-the-go, in the activity or with friends, what who how and why do you want to know about? ex I am curious about the pictures every one took in my wedding. It is the important moment in my life and I want to know every detail.