The screenshot above is 90+ high res avatars in High Fidelity in a small shared space while also kitted out in VR rigs. As anyone who's tried Second Life (or any other MMO for that matter) can tell you, this would be nigh impossible without hellacious, grotesque lag. Indeed, VR evangelist Robert Scoble argues that's the key reason SL never went mass market. I don't quite agree with that*, but it's definitely true that the first social VR platform to master high quality high concurrency will have a key advantage over others. According to HiFi founder Philip Rosedale, High Fidelity has done just that.
In the image above there are 90 people together, most of them with HMD's and hand controllers (either Vive or Rift + Touch). This is a lot of data moving around: Each person generates 100Kbps of compressed audio from their microphone which is sent to the audio server, and also about 200Kbps of joint motion data, which is sent to the avatar server. That is about 30Mbps received by the servers. The output from the servers was about 270Mbps, or about 3Mbps per receiver... Latency has to stay low for everyone to feel connected (with each other and the performers). In this event, most people were experiencing a latency of between 100 and 150 milliseconds - the time delay between motion or sound from their actual bodies being seen by others.
Very impressive, if the average High Fidelity user can replicate this too. Which Philip is challenging them to do -- which turns out to be a surprisingly cost-effective stress test:
Try it yourself: If you want to host a 100-person event with High Fidelity, you will need to use a server with at least 50Mbps upstream (to your server) and at least 500Mbps downstream. For this test we used an Amazon c4.xlarge instance for the avatar, entity, and message servers, and a c4.4xlarge instance for the audio mixer (which is the most heavily loaded). As a side-note, bandwidth and CPU are getting really cheap: the Amazon hosting cost of a two hour 100-person event run this way was only about $4.50!
I'd say that's more than a side note, because that cost is likely to come down even more in coming years.
* Why I think the lack of high concurrency didn't hurt Second Life: Linden Lab insiders tell me something on the order of 95% of new SL account users quit on the first try well before they even got to a social area with more than a few avatars -- and for those who did get that far, often crowds contributed to their sense of feeling overwhelmed and intimidated, and also discouraged them to stay. Meanwhile, Minecraft went mass market even though (correct me if I'm wrong, 'Crafters) only a couple dozen users typically log into the same server. To Scoble's point, however, I suppose you could make the case that if Second Life could host packed live music concerts and other kinds of big crowd-based content, many more would have been encouraged to check it out.