WordPress at a glance
filter is not described

blog_option_(option) filter-hook . WP 3.5.0

Filters a blog option value.

The dynamic portion of the hook name, $option, refers to the blog option name.

Usage

add_filter( 'blog_option_(option)', 'filter_function_name_1021', 10, 2 );
function filter_function_name_1021( $value, $id ){
	// filter...

	return $value;
}
$value(string)
The option value.
$id(int)
Blog ID.

Where the hook is called

get_blog_option()
wp-includes/ms-blogs.php 688
return apply_filters( "blog_option_{$option}", $value, $id );

Where the hook is used (in WP core)

Does not used.