Its interesting how drupal use cases stumps you even after
years. I was wondering how would one place the same block (lets say
user login block) in different regions on different pages (block
visibility) in the same theme of course. This question just popped
without any req for client work, so there is no urgency but yeah it
would be great to know solutions to this use case. I found
http://drupal.org/project/multiblock
which allows you to create multiple instances, I dont know the
internals so dont know how efficient it is, though usage statistics are
pretty good for this module.