Example, not global:

Thanks Steevb, I'm actually looking for something that will limit the type of blocks that a user can add, not necessarily the number of blocks. Something like:
<?php
$a = new Area('Something');
$a->setAllowedBlockTypes(array('block handle or id','block handle or id'));
$a->display($c);
?>

I'm pretty sure it's not possible, but wanted to reach out to the community to see if anyone has done something like this before.

Thanks!

Sorry, my mistake, should have read post properly!!!

I don't think you can do it short of overriding some core files and inserting your own code, in which case you may as well use permissions.

If you don't want the hassle of going through permissions piecemeal in the sitemap, you could look into writing code to set the permissions.