There is a need for shared virtual spaces for events, specifically events where the participants do not know each other a priori and this is a particular strength of the Second Life model. You have the network effect of many people combined with a shared virtual space. At Cisco, we use this function frequently to have focus groups, product launches, and press conferences. This allows for a bi-directional exchange of ideas from an ad-hoc group of attendees in a manner that you cannot achieve with other technology solutions. If we use traditional voice bridges, then you need to mute the participants during the 'presentation', and the experience is pretty spartan......if you use web conferencing, you achieve a richer media experience but lose the intimacy of horizontal interaction (where the speaker to attendee is 'vertical interaction', but attendee to attendee is 'horizontal interaction', like students passing notes and whispers in undergraduate Biology class lecture). This is where shared virtual spaces shine.
I still believe that there needs to be widespread deployment of standard protocols, like COLLADA, however am skeptical that the business rationale is there for anyone to abandon the walled-garden model we see in current virtual world implementations (OpenSIM excluded). The wildcard is if the 3D conferencing and small event space vendors, led by companies like Transmutable and Qwaq, end up stealing the aforementioned (juicy/lucrative) shared virtual spaces business from public social worlds.