So you can have anyone fulfilling these roles. At present there are somewhere around 60 data servers with one large one we run; one aggregator infra; and probably around 10 actively developed clients. We hope to see all of these roles expand over time, but a likely stable future will see about as many aggregator infrastructure as the Web has search engines.
When we say an infrastructure takedown, we mean off the aggregator and the data server we run. This is high impact but not total. The user could migrate to another data server and then use another infra to persist. If we ever fail (on policy, as a business, etc) there is essentially a pathway for people to displace us.
Sorry about going off-topic, I realise it's only tangentially about labelling.
But if it's already working (because you're running an aggregator), there doesn't seem much reason for anyone else to run one? In other words, isn't there a significant risk that there will be fewer aggregators than there are search engines, i.e. just a single one?
It might not be necessary or useful to have multiple aggregators right now. However, I do feel better knowing that if Bluesky the company goes under or changes to a degree where I'm not happy with their decisions, it's possible for someone to stand up a second aggregator.
For that matter, if someone's a free speech absolutist and if they care enough about it to spend the money, they could stand up an aggregator right now with more permissive standards.
Running an "AppView" (an atproto application aggregator/indexer/API server) is generally an order of magnitude more expensive and complicated. But still not beyond the reach of a user coop, non-profit, or small startup.
So these services should all be well within the capabilities of at least multiple companies operating in the atproto ecosystem as it scales.
And in many cases it should make good sense for these companies to do this since it will improve their performance by colocating their services and enable them to do things like schedule their own maintenance windows, etc.