Secondary indexes

[Mark]

I haven't looked at Cassandra since 0.6.6 and now I notice in 0.7+ there 
is support for secondary indexes. I haven't found much material on how 
these are used and when one should use one. Can someone point me in the 
right direction.

Also can these be created (and deleted) as needed without affecting the 
underlying CF? If so, I'm guessing there is no need to create another CF 
just for indexing. What are the disadvantages of this method?

Thanks all.