[TL;DR: A long tail is needed for distributed technology to be sustainable I think, otherwise it’s just centralisation and single points of failure in a different form. A long tail means the bottom 80% take over 50% of a market, and the top 20% under 50%. Mastodon currently has over 85% of its participants in the top 20% of instances, and it’s worse than that as 77% of participants are in 0,7% of instances. Just 15% are in the bottom 80% of instances. There’s a power law distribution, but it’s not a long tail. What can Mastodon do to get there and to sustainability?]

On 6 October 2016 Mastodon was launched, and its originator Eugen Rochko looks back in a blogpost on the journey of the past two years.

I joined on 7 April 2017, 6 months after its launch, at the Mastodon.cloud instance. I posted some messages for a month, then fell quiet for half a year. A few messages last March, and then I started using it more frequently last month, in the run-up to figuring out how to run Mastodon for myself (which for now means a hosted solution, but still aiming for running it from the home router). It’s now part of my daily information diet, but no guarantee yet it will last, although being certain I have ‘my half’ of the conversation on a domain I own helps a lot towards maintaining worthwhile exchanges.

Eugen’s blogpost is rightfully proud of what has been accomplished. It’s not yet proof of the sustainability of federated solutions though as he suggests.

He shares a few interesting numbers about the usage of Mastodon. The median of the 3460 known instances is 8 users. In total there are 1.627.557 registered accounts. The largest instance has 415.941 members, while the top 3 together have 52% of users, meaning the number 2 and 3 average 215.194 accounts. The top 25 largest instances have 77% or 1.253.219 members, meaning that the numbers 4-25 average 18.495 users. As the median is 8 it means the smallest 1730 instances have at most 8*1730 = 13.840 users. It also means that the number 26 to number 1730 instances have at least 360.498 members, or an average of 211. This tells us there’s a Pareto power law distribution: the top 20% of instances hold at least 85% of users at the moment. That also means there is no long tail, just a stub that holds at most 15% of Mastodon users only. For a long tail to exist, the smallest 80% of instances should account for over 50% of users, or over three times more than the current number.

As the purpose of Mastodon is distribution, where federation allows everyone to connect regardless of their instances (sort of like e-mail), I think Mastodon can only be deemed sustainable if there is a true long tail. Meaning, that while the number of users goes up, the number of instances should go up at a faster rate. So that over 50% of all Mastodon users will be on the 80% smallest or even individual instances. In the current numbers we should be most interested in the 50% of instances that now have 8 or less users, and find out what drives those instances, so we may have many many more of them. We should also think about what a bigger-to-smaller-instances funnel for members can look like, not just leave it to chance. I think that the top 25 Mastodon instances, which is just 0.7% of the total, currently having 77% of all users is very problematic from a sustainability perspective. Because that level of concentration is completely at odds with the stated purpose of Mastodon: distribution.

Eugen Rochko in his anniversary posting points at a critical article from April 2017 in Mashable, implying that criticaster has been been proven wrong definitively. I disagree. While much of the ‘predictions’ in that article are indeed silly, it also contains a few hints as to where sustainability may be found. The criticaster doesn’t get federation (yet likely uses mail everyday), and complains about discovery (yet likely is relieved not all his personal e-mail addresses are to be found in Google). Yet if we can’t explain distribution and federation, and can’t or don’t communicatie how discovery works in such a setting then we won’t be able to make a long tail grow. For more people to adopt small or individual instance we need to bring the threshold for running your own instance way down, and then way down again. To the level of at most one click installing a script on any regular hosting service, and creating a first account.

Using open protocols, like ActivityPub which Mastodon supports, is key in getting more people out of walled gardens and silos, and on the open web. Tracking its adoption is a useful measure of success, but 2 years of existence is not a sign of sustainability at all. What Eugen Rochko has kicked off with Mastodon is valuable and very laudable, but we have barely started getting to where we need to be for it to stick.