What is a cell group supposed to be?

From the Small Group Leader's Handbook, written by a small group (Intervarsity),

"Here's what we mean when we say 'small group.'  

A small group is a transformational community that studies the Bible, prays and participates in God's mission together for the purposes of God's transforming work.

Notice that the vision for small groups has transformational community at its center. not cheap community. Not virtual community. Not what-we-happen-to-have-in-common-at-the-moment community. Not small-talk-in-passing community. Not community when it's convenient. Transformational community."