Re: Online Members Widget max number
It is up to each widget (plugin) developer to determine whether or not their widgets are compatible with the new widget API. In theory, WPMU 2.8.1 should offer backwards compatibility with older widgets. But, it is not always the case.
In term of BuddyPress’ widgets, I’m not sure when they will be updated. If we get sufficient number of reports of their improper functioning, then we will of course fix the issue. So, if you are having issues with the widgets that come with BP, please let us know. This post is a good example!
In general, if you have a 3rd-party widget that is not working in 2.8.1, please contact the developer directly and ask when they plan to upgrade.