Features_extra: after enabling fe_block, no Machine Name field appears on block edit form
The fe_block module only allows exporting blocks represented in the boxes table — those created via the admin/build/block/add user interface.

Exportable blocks will have block as the second-to-last component of the admin URL:


Blocks created using, say, Views, or a module's hook_block() implementation, however, are not exportable using fe_block — it doesn't make sense to export blocks such as those, since Views provides its own export mechanism, and other module-owned blocks are already in code to begin with.