Drupal 7 will consider "node" $content as a block region, which has advantages over the old "special" $content variable in Drupal 6.

Now since the $content is a block region, themer no longer needs to provide special region area in top / bottom of the node, a site builder just have to put the "top node" block in the content region and set it to be on top / bottom of the content block.

But how about if you want to "integrate" the content node block with other block region, like if you want to display a "node" content on left top while providing another custom region on the left bottom of the node while printing the rest of the node content on the right side??

Sounds complex? In drupal 6, we can achieve this by invoking

theme('blocks', 'your_block_region_machine_name');

Now in Drupal 7, theme_blocks is gone... so to achieve the same result we need to invoke this instead :

print render(block_get_blocks_by_region('your_block_region_machine_name'));

The better way to get this done in Drupal 7 is by invoking the function inside preprocess_node function like this :

function your_theme_name_preprocess_node(&$variables) {
	if ($blocks = block_get_blocks_by_region('your_block_region_machine_name')) {
      $variables['banner_space'] = $blocks;
  }
}

Additional information provided by aquariumtap if you want to preprocess the block region directly from template.php instead of theme.info files :

aquariumtap : If you want those blocks to be available to hook_preprocess_region, add a bit more information:

function your_theme_name_preprocess_node(&$variables) {

if ($blocks = block_get_blocks_by_region('your_block_region_machine_name')) {
  $variables['banner_space'] = $blocks;
  $variables['banner_space'] = $blocks;
  $variables['banner_space']['#theme_wrappers'] = array('region');
  $variables['banner_space']['#region'] = 'your_block_region_machine_name';
  }
}

then invoke this function inside your node.tpl.php

 
  print render($banner_space); ?>

If you got better way to do this, please post it in your comment :)