consumer groups

Hi,

I am planning to use kafka for a work queue type use case with multiple
consumers. I also plan to use it with multiple consumer groups. What is not
clear to me from the documentation is how to define+manage consumer groups
or if that is possible at all. It appears to me that a consumer group is
created just by connecting with a new group-id. What is not clear to me is
how to manage this: if I no longer want a consumer group how do I remove
it? What happens when there are no consumers of a group listening? If all
the consumers stop listening how long will Kafka continue to store messages
for that group?

Thanks for any clarification,

Greg Lloyd