This is a test plugin that can only be network activated.

eb-network-activate-plugin.php

<?php

/*
Plugin Name: Network Activated Plugin Only
Plugin URI: http://wordpress.org/extend/plugins/hello-dolly/
Description: This plugin can only be network activated. And therefore it doesn't show up single site network admin page.
Author: Enej Bajgoric
Version: 1
Network: true
*/

// This just echoes the chosen line, we'll position it later
function  eb_network_activated_plugin_notice() {
	echo "<p id='eb-network-actiated-text'>I am network Activated!</p>";
}

// Now we set that function up to execute when the admin_notices action is called
add_action( 'admin_notices', 'eb_network_activated_plugin_notice' );

// We need some CSS to position the paragraph
function eb_network_activated_plugin_css() {
	// This makes sure that the positioning is also good for right-to-left languages
	$x = is_rtl() ? 'left' : 'right';

	echo "
	<style type='text/css'>
	#eb-network-actiated-text {
		float: $x;
		padding-$x: 15px;
		padding-top: 5px;		
		margin: 0;
		font-size: 11px;
		color:red;
	}
	</style>
	";
}

add_action( 'admin_head', 'eb_network_activated_plugin_css' );