BuddyPress.org

@cocomozlo

Have you seen Brajesh’s Sitewide Footer Content plugin? It’s a premium plugin fromBuddyDev.com so you have to sign up to get it, but he’s got a lot of goodies there which make the $30 (for 3 months) a pretty good investment.

http://buddydev.com/plugins/buddypress-premium-plugins/sitewide-footer-content-plugin-for-wpmubuddypress/

I use it on my network (with subdirectories mind you) but know of others who use it with subdomains with no problem reported.

Hope this helps!