To facilitate events in Second Life or Opensim across multiple sims or regions (usually adjacent regions, often at the 4 corners of 4 simulator regions "4-sims", but can be disjoint regons) technology is required to relay and share the various modalities for the event.
Group membership can facilitate a range of communication and management functions for events. This include grouyp instant messaging and voice which work anywhere across all regions in Second Life, and do not vary in level by distance or have cut off communication ranges as is the case with spatialized voice and text chat, etc. It can be convenient to have a way to rapidly join a group on entering an event to make management easier. A script in an object can allow avatars to join themselves into open membership groups.
Voice in Second Life (Vivox) and Opensim (usually Freeswitch) works on a per region basis when used in an open spatialized context. Group voice can be used and works across multiple regions wherever the avatar is located.
Video/media URLs are on a per plot basis in Second Life (one URL per plot). Opensim is more flexible in terms of media URLs. New technology for media plug ins is forthoming in Secid Life as at October 2009. Screens on adjavcent plots that can be seen by an avatar look to be showing the same URL as on the plot that the avatar is placed in. Technlogy can be used to relay the URL that is to be seen by avatars on different plots by sending messages between scripts in objects to specific "relay" objects (which must be deeded to the group which owns the land for group owned plots) which change the pot media URL (object to object IM using their UUID) from a "master" controller.
Text-based local chat in Second Life has a range of 20m and works over several regions. Shout allows for 100m range. To go across multiple regions, instant message must be used, which can work with groups. Or else technoogy is required to relay text chat in and out in 20m diameter cshperes... difficult, but not impossible, to arrange with text-cancelling linked chat relays, which can also act as conduits to external web-based chat systems (like OpenVCE.net I-Say) and text chat loggers (which must respect the Linden Labs terms of Service in terms of asking for permisison before relaying any text chat and potentially private content outside of Second Life).