WordPress MU

What's the right way to activate buddypress on a site other than the current one? I've tried switching to the site with:
switch_to_blog( $blog_id );

... but activate_plugin("buddypress/bp-loader.php") fails (returns nothing).

So how can I activate buddypress for say "site1.domain.com" when the php script is run from "domain.com"?

setting $_SERVER['HTTP_HOST']="site1.domain.com" before you load the wp env does the trick :)

Um, there's other ways to do this built right in to BP. their forums have it.

I was resorting to those hacks because switching to the blog and updating the active_plugins option wasn't working for some reason. Then magically it started to work. Go figure. Is this the other way you were thinking of or is there an even a simpler way?

switch_to_blog($blog_id);
update_option('active_plugins', array( "buddypress/bp-loader.php" ));
restore_current_blog():

Let's go back to what you're originally trying to do. You want to run BP off something *other* than the main blogs, or as well as?

Because that's two different answers. Neither one of which is what you did. Don;t use switch to blog. This is *built in* to BP and you're looking for hard answers when it's really easy. (and all over their site)

From here:
http://codex.buddypress.org/how-to-guides/changing-internal-configuration-settings/

Set which blog ID BuddyPress will run on:
define ( 'BP_ROOT_BLOG', $blog_id );

Allow BuddyPress to function on multiple blogs of a WPMU installation, not just on one root blog:
define ( 'BP_ENABLE_MULTIBLOG', true );

Thanks Andrea. I'm using yours and ron's multi-site plugin. When a new site is created, I want buddypress to be automatically enabled with it.

In the ra_add_site() function I simply call:
update_option('active_plugins', array( "buddypress/bp-loader.php" ));

Works like a charm. Thanks for your constant support and apologies for the confusion :)