The latest myblocksadmin supports cloning blocks.
It's quite easy.
After installing myblocksadmin into your module, append a line.
$modversion['blocks'][(block_number)]['can_clone'] = true ;
That's all!
Of course, the latest myblocksadmin is secure and easy to use.
To all module developpers: why not try it!
As you know, cloning block was implemented in TinyD mh014.
But the old implementation was TinyD dependent, and other modules can't use it.
The latest one is module independent.
It is usable for almost modules which has block(s).